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ST-segment elevation in right precordial leads implies depressed right ventricular function after acute inferior myocardial infarction
ST-segment elevation in right precordial leads implies depressed right ventricular function after acute inferior myocardial infarction Hideaki Yoshino, MD, Hiroshi Udagawa, MD, Hisashi Shimizu, MD, Eisei Kachi, MD, Tatsuto Kajiwara, MD, Kohei Yano, MD, Masato Taniuchi, MD, and Kyozo Ishikawa, MD Tokyo, Japan
Background The prognosis of acute inferior myocardial infarction is worse when it is complicated by right ventricular infarction. ST elevation in the right precordial leads is one of the reliable methods for detecting acute right ventricular infarction. The purpose of the study was to examine the relation between ST elevation in the right precordial electrocardiographic leads during acute inferior infarction and the severity of right ventricular systolic dysfunction.
Methods This study analyzed the relation between ST elevation ≥0.1 mV in V4R and the severity of right ventricular systolic dysfunction in 43 consecutive patients (men/women: 35/8; average age 62 ± 9 years) with acute inferior myocardial infarction with a rapid-response Swan-Ganz catheter to measure the right ventricular ejection fraction (RVEF). Results RVEF was significantly lower in patients with ST elevation (n = 18) than in those without (n = 25) (33% ± 6% vs 40% ± 9%, p = 0.010). If the infarct-related lesion was located in the proximal right coronary artery, RVEF tended to be lower than if the lesion was located in the distal right coronary artery or the left circumflex coronary artery (33% ± 10% vs 37% ± 9% vs 42% ± 9%, p = 0.101). Logistic regression analysis demonstrated that ST elevation in V4R was the only independent predictor of depressed RVEF (odds ratio = 5.31, 95% confidence interval = 1.28 to 22.1, p = 0.022).
Conclusion ST elevation in lead V4R during acute inferior myocardial infarction predicts right ventricular systolic dysfunction. (Am Heart J 1998;135:689-95.)
Although right ventricular infarction was first described more than 60 years ago,1 it has not attracted much clinical attention until recently. Corn et al.2 reported in 1974 that hemodynamics deteriorate markedly and atrioventricular block tends to occur in patients with right ventricular infarction, with a resulting increase in the hospital death rate.3,4 Therefore it is critical to determine early whether right ventricular infarction is present and to initiate appropriate therapy as soon as possible. Although the hemodynamic abnormalities of patients with a typical right ventricular infarction are well understood,5 right ventricular function including right-sided hemodynamics immediately after the onset of inferior infarction remains to be understood clearly. The diagnosis of right ventricular infarction can be based on electrocardiographic (ECG) changes,3,6-13 From the Second Department of Internal Medicine, Kyorin University School of Medicine. Submitted Feb. 24, 1997; accepted Jan. 9, 1998. Reprint requests: Kyozo Ishikawa, MD, Second Department of Internal Medicine, Kyorin University School of Medicine, 6-20-2 Shinkawa, Mitaka, Tokyo 181, Japan. Copyright © 1998 by Mosby, Inc. 0002-8703/98/$5.00 + 0 4/1/88734
echocardiography,14-20 radionuclide angiography,21-25 pyrophosphate myocardial scintigraphy,21 or right ventricular catheterization.2,26,27 Of these methods, right precordial ECG leads provide the simplest and most objective data in the acute stage of infarction. However, a method of quantitatively evaluating right ventricular systolic function during acute right ventricular infarction has not yet been developed. Echocardiography and right ventricular angiography are commonly used to evaluate right ventricular systolic dysfunction, but the interpretation of echocardiograms is subjective, and right ventricular angiograms are inappropriate for serial measurement. Furthermore there have been no direct, simultaneous, and quantitative comparisons of the relation between changes in the right precordial ECG leads and right ventricular systolic dysfunction after acute right ventricular infarction. The recently developed rapid-response Swan-Ganz catheter system28-31 enables reproducible measurement of the right ventricular ejection fraction (RVEF).32,33 With this catheter system we determined the relation between right ventricular function and ST elevation in lead V4R during acute inferior myocardial infarction.
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Methods Patients Forty-three consecutive patients (35 men, 61.4 ± 8.6 years of age [mean ± SD], range 41 to 80 years) satisfying the inclusion criteria described in the following text were selected from a series of 56 consecutive patients admitted for a first acute inferior myocardial infarction to the coronary care unit of Kyorin University Hospital within 6 hours after the onset of typical chest pain. The inclusion criteria included (1) age ≤80 years, (2) successful insertion of a modified triple-lumen Swan-Ganz catheter with intracardiac electrodes and a rapidresponse (100 msec) thermistor (model 93A-431H-7.5F, Baxter Healthcare Co., Irvine, Calif.) within 2 hours after arrival in the emergency department, and (3) identification of the infarct-related artery by emergent coronary angiography and achievement of successful reperfusion. This study was done prospectively. Standard 12-lead electrocardiograms and right precordial electrocardiograms (leads V3R through V6R) were recorded immediately after the patient was admitted to the emergency department. Right ventricular infarction was defined by ST-segment elevation ≥0.1 mV in lead V4R. Blood samples for the measurement of creatine phosphokinase activity were collected every 3 hours until a peak value was obtained.
Reperfusion therapy and left heart catheterization The delay between the diagnosis of acute myocardial infarction and reperfusion therapy was generally less than 1 hour. Cardiac catheterization was performed with the Seldinger technique, and coronary angiograms were obtained in multiple views in a routine manner by the Judkins technique. After occlusion (total or subtotal) of the vessel supplying the infarct zone was confirmed, emergency primary percutaneous transluminal coronary angioplasty (PTCA) or coronary thrombolysis with tissue-plasminogen activator (alteplase) administered through a selective coronary catheter was performed. In six patients coronary thrombolysis with intravenous infusion of tissue-plasminogen activator was performed. In these patients the infarct-related lesions were confirmed by emergency coronary angiography at the end of reperfusion therapy. Patients with unsuccessful thrombolysis (Thrombolysis in Myocardial Infarction flow34 grade 0 to 1) underwent rescue PTCA. Successful reperfusion was defined as an improvement in coronary flow to Thrombolysis in Myocardial Infarction grade 2 or 3 flow. In seven patients the coronary blood flow was Thrombolysis in Myocardial Infarction flow grade 2 or better at the time of initial coronary angiography. In these patients coronary angiography was terminated without reperfusion therapy. Written informed consent was obtained from each patient after the risks and potential complications of cardiac catheterization and reperfusion therapy were explained appropriately. Among the 39 patients who did not require an intraaortic balloon pump, 11 patients achieved reperfusion with tissue-plasminogen activator and had an RVEF of 36.5% ± 7.5%, whereas 21
patients underwent PTCA and had an RVEF of 36.0% ± 8.1%. Seven patients who had spontaneous coronary reflow without reperfusion therapy had an RVEF of 38.6% ± 12.7%.
Measurement of right heart hemodynamics and right ventricular ejection fraction Right heart catheterization was performed through the right femoral vein immediately after coronary reperfusion therapy at the catheterization laboratory. A modified triplelumen Swan-Ganz catheter32,33 with intracardiac electrodes and a rapid-response thermistor was advanced until the tip was in the pulmonary artery. The pressure from the proximal lumen was monitored to ensure that the proximal port of the catheter was in the right atrium. The right atrial pressure, pulmonary arterial pressure, and pulmonary capillary wedge pressure were monitored. To determine right ventricular volumes, a rapid manual injection of 5 ml cold saline solution (1° C to 5° C) was performed through the proximal port. Data from the thermodilution curves were processed by a computer system (American Edwards Laboratory, Santa Ana, Calif.) together with an electrocardiographic signal for the determination of heart rate, cardiac output, right ventricular end-diastolic volume index, right ventricular end-systolic volume index, stroke volume index, and RVEF.
Logistic regression analysis Seven clinical variables were used for multivariate logistic regression models to identify correlates of the binary response variable (RVEF <35%). The variables examined included right atrial pressure, systolic pulmonary pressure, ST elevation in lead V4R, use of reperfusion therapy, use of intravenous pressor therapy, residual stenosis in the infarctrelated artery, and location of the infarct-related lesion.
Statistical analysis Statistical analysis was performed with StatView 4.11. Logistic regression was done with “LOGISTIC REGRESSION” from SPSS for Macintosh (Version 6.1J). Data are expressed as the mean ± SD. Comparisons between two groups were performed with the unpaired Student’s t test. Statistically significant differences among three groups were determined by one-way analysis of variance (ANOVA) followed by Bonferroni’s procedure if the ANOVA probability value was <0.05. A chi-squared test was used for comparison of categoric data. Results were considered statistically significant if p < 0.05. The odds ratios, 95% confidence intervals, and p values of the final model (i.e., after adjustment for all other significant covariates) are reported.
Results ST elevation in lead V4R and clinical characteristics The ST elevation and non-ST elevation groups did not differ significantly in terms of baseline clinical
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characteristics (Table I) except for the heart rate (p = 0.004), cardiac index (p = 0.024), and peak creatine phosphokinase activity (p = 0.046). All of the patients in the ST elevation group received acute reperfusion therapy (angioplasty or thrombolytic therapy), whereas seven (28%) patients in the non-ST elevation group received no reperfusion therapy because they had confirmed reflow at the time of emergency coronary angiography (p = 0.046).
ST elevation in lead V4R and right ventricular dysfunction The RVEF was significantly lower and the right ventricular end-systolic volume index was significantly greater in the ST elevation group than in the non-ST elevation group (Table I). However, the right ventricular end-diastolic volume index did not differ significantly between the two groups. No other significant differences were seen in hemodynamic indexes between the two groups except heart rate and cardiac index. Pressors such as dopamine and dobutamine were given to 8 (44%) of 18 patients in the ST elevation group and to 6 (24%) of 25 patients in the non-ST elevation group. Right ventricular function without the effect of pressors was compared between the two groups after patients who received pressors were excluded (Table II). The ST-elevation group (n = 10) had a lower RVEF (p < 0.001), a higher right ventricular end-diastolic volume index (p = 0.025), and a higher right ventricular end-systolic volume index (p = 0.006) compared with the non-ST elevation group (n = 19). No other significant differences were found in all hemodynamic indexes between the two groups. An intraaortic balloon pump was used in 3 (17%) of the 18 patients in the ST elevation group and 1 (4%) of the 25 patients in the non-ST elevation group to augment blood pressure. In the ST-elevation group the RVEF of the 3 patients requiring intraaortic balloon pump insertion tended to be higher than in the 15 patients who did not require an intraaortic balloon pump (38.7% ± 3.8% vs 31.9% ± 5.8%). Therefore those patients requiring an intraaortic balloon pump were excluded, and right ventricular function was compared between the ST elevation group (n = 15) and the non-ST elevation group (n = 24). Significant differences were noted between the ST elevation group and the non-ST elevation group with respect to RVEF (31.9% ± 5.8% vs 39.5% ± 9.0%, p = 0.006), right ventricular end-systolic volume index (87 ± 41 ml/m2 vs 65 ± 23 ml/m2, p = 0.036), heart rate (88.7 ± 18.1
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Table I. Clinical and hemodynamic characteristics of patients with or without ST-segment elevation in lead V4R ST elevation (+) (n = 18) Male/female Age (yr) Risk factors Smoking (%) Hypertension (%) Diabetes mellitus (%) Hyperlipidemia (%) Additional therapy DOA/DOB (%) IABP (%) Reperfusion therapy (%) PTCA tPA Conservative Infarct-related artery (%) RCA proximal RCA distal LCx Coronary stenosis (% stenosis) Before reperfusion No. of diseased vessels (%) One Two Three Combined with LAD lesion (%) Peak CPK (IU/L) Right ventricular function RVEF (%) RVESVI (ml/m2) RVEDVI (ml/m2) RVSVI (ml/m2) Hemodynamic parameters BP systole (mm Hg) Heart rate (beats/min) RAP (mm Hg) PAP systole (mm Hg) PAP diastole (mm Hg) PCWP (mm Hg) CI (L/min/m2)
ST elevation (-) p (n = 25) Value
13/5 60.3 ± 8.4
22/3 62.3 ± 8.7
NS NS
72 61 44 33
70 61 17 26
NS NS NS NS
44 17
24 4
NS NS 0.046
67 33 0
52 20 28
50 44 6
36 44 20
98.4 ± 3.3
99.5 ± 0.5
NS
NS NS
56 33 11 22 4670 ± 3428
60 16 24 32 NS 2313 ± 1649 0.005
33.1 ± 6.0 85.1 ± 37.6 122.7 ± 42.1 38.7 ± 8.6
39.6 ± 8.8 0.010 65.7 ± 22.9 0.042 104.7 ± 25.4 NS 39.2 ± 8.5 NS
123 ± 16 91.5 ± 17.7 6.1 ± 2.8 22.6 ± 4.9 12.9 ± 3.9 11.4 ± 3.5 3.47 ± 0.91
127 ± 9 NS 77.8 ± 11.7 0.004 6.7 ± 4.2 NS 21.5 ± 5.1 NS 12.5 ± 3.6 NS 10.0 ± 4.0 NS 2.95 ± 0.54 0.024
NS, Not significant; DOA/DOB, dopamine and/or dobutamine; IABP, intraaortic balloon pump; RCA proximal, proximal segment of right coronary artery; RCA distal, distal segment of right coronary artery; LCx, left circumflex coronary artery; LAD, left anterior descending coronary artery; CPK, creatine phosphokinase; RVESVI, right ventricular endsystolic volume index; RVEDVI, right ventricular end-diastolic volume index; RVSVI, right ventricular stroke volume index; BP systole, systolic blood pressure; RAP, right atrial pressure; PAP systole, systolic pulmonary arterial pressure; PAP diastole, diastolic pulmonary arterial pressure; PCWP, pulmonary capillary wedge pressure; CI, cardiac index.
beats/min vs 77.8 ± 12.0 beats/min, p = 0.028), and peak creatine phosphokinase activity (4130 ± 3472 IU/L vs 2343 ± 1677 IU/L, p = 0.037).
Infarct-related lesion and right ventricular function The RVEF was lower and the right ventricular enddiastolic volume index and right ventricular end-sys-
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Table II. Hemodynamic characteristics of patients who did not require infusion of dopamine or dobutamine
RVEF (%) RVEDVI (ml/m2) RVESVI (ml/m2) BP systole (mm Hg) Heart rate (beats/min) RAP (mm Hg) PAP systole (mm Hg) PAP diastole (mm Hg) PCWP (mm Hg) Cardiac index (ml/m2)
ST elevation (+) (n = 10)
ST elevation (-) (n = 19)
31.0 ± 6.7 133.9 ± 53.9 95.5 ± 47.8 126.6. ± 15.9 81.7 ± 11.6 5.4 ± 2.2 22.2 ± 5.4 11.0 ± 2.5 11.9 ± 4.4 3.06 ± 0.86
41.4 ± 6.7 98.2 ± 22.8 59.1 ± 17.8 128.2 ± 9.5 77.2 ± 12.7 6.1 ± 4.0 21.8 ± 5.5 12.2 ± 3.8 9.8 ± 3.8 2.92 ± 0.48
p Value <0.001 0.025 0.006 NS NS NS NS NS NS NS
NS, Not significant; DOA/DOB, infusion of dopamine and/or dobutamine; RVEDVI, right ventricular end-diastolic volume index; RVESVI, right ventricular end-systolic volume index; BP systole, systolic blood pressure; RAP, right atrial pressure; PAP systole, systolic pulmonary arterial pressure; PAP diastole, diastolic pulmonary arterial pressure; PCWP, pulmonary capillary wedge pressure.
tolic volume index tended to be greater, although not significantly, when the lesion was in the proximal portion of the right coronary artery (n = 17) compared with lesions in the distal right coronary artery (n = 19) or in the left circumflex coronary artery (n = 7) (Table III). No difference in RVEF was noted with respect to the method of reperfusion (angioplasty vs thrombolysis vs spontaneous reflow, 36.0% ± 8.1% vs 36.5% ± 7.5% vs 38.6% ± 12.7%, respectively).
Logistic regression analysis The factors associated with a lower RVEF were examined by logistic regression analysis. Only ST elevation in V4R was significantly associated with an RVEF <35% (odds ratio = 5.31, 95% confidence interval = 1.28 to 22.1, p = 0.022).
Discussion At present no method exists for evaluating right ventricular systolic function quantitatively in patients with acute myocardial infarction. However, rapidresponse Swan-Ganz catheter systems allow for the continuous measurement of RVEF, which can be used as an indicator of right ventricular systolic function during acute myocardial infarction.32,33 Analysis of the relation between the RVEF obtained by this method and ST elevation in V4R in this study demonstrates that the RVEF was significantly lower in patients with ST elevation.
Right ventricular infarction The prognosis worsens and the morbidity rate increases for patients with inferior myocardial infarc-
tion when right ventricular infarction is also present during the acute stage.36 According to Zehender et al.3,37 the hospital death rate reaches 30% or more in patients with an inferior myocardial infarction complicated by right ventricular infarction that is not treated with reperfusion therapy. Even in the setting of mild left ventricular systolic dysfunction, these patients tend to have hemodynamic abnormalities and have shock at a high frequency.4 Right ventricular infarction is diagnosed by ST elevation in leads V3R or V4R5,10-13 and by the evidence of right ventricular enlargement,14 abnormal right ventricular wall motion, and paradoxical movement of the interventricular septum15-18 on two-dimensional echocardiography or increased right heart filling pressure determined by right heart catheterization.2,26,27 The diagnosis of right ventricular infarction in the subacute stage is primarily based on the detection of right ventricular systolic dysfunction on radionuclide angiography.7,22,23,25 During the very acute stage of infarction, ST elevation in lead V4R is considered to be superior with respect to diagnostic accuracy and simplicity.4,8,11
Evaluation of right ventricular function Echocardiography and right ventricular contrast angiography are generally used to evaluate right ventricular systolic function. However, echocardiography has a limited capability to evaluate right ventricular systolic function quantitatively, although it is useful for assessing the hemodynamic abnormalities that accompany right ventricular infarction. In addition, right ventricular angiography is not suitable for serial evaluation
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Table III. Location of the infarct-related lesion and right ventricular function
RVEF (%) RVEDVI (ml/m2) RVESVI (ml/m2) Cardiac index (L/min/m2)
Prox RCA (n = 17)
Dist RCA (n = 19)
LCx (n = 7)
32.7 ± 10.0 140.3 ± 99.7 102.4 ± 99.6 3.26 ± 0.94
37.2 ± 8.9 108.7 ± 39.6 71.6 ± 37.6 2.96 ± 0.69
41.6 ± 9.2 106.0 ± 21.2 64.7 ± 17.7 3.33 ± 0.42
p Value NS NS NS NS
NS, Not significant; Prox RCA, patients with proximal right coronary artery lesions; Dist RCA, patients with distal right coronary artery lesions; LCx, patients with left circumflex coronary artery lesions; RVEDVI, right ventricular end-diastolic volume index; RVESVI, right ventricular end-systolic volume index.
of right ventricular systolic function. Elevation of the right ventricular filling pressure, that is, an increase in the mean right atrial pressure, is an important criterion for the diagnosis of right ventricular infarction. However, the diagnostic accuracy of this factor is limited because the mean right atrial pressure quickly falls if fluid replacement is insufficient or if diuretics are used. Furthermore this study demonstrated that even in patients with ST elevation and a reduced RVEF, which are clear indications of right ventricular systolic dysfunction, increased right atrial pressure was rarely observed. A right atrial pressure ≥10 mm Hg was noted in 1 (6%) of the 18 patients in the ST elevation group and in 5 (20%) of the 25 patients in the non-ST elevation group. Previous studies22,23 have suggested that radionuclide angiography is the gold standard for the evaluation of right heart function, because it allows for the analysis of right ventricular systolic abnormalities by phase analysis in patients with right ventricular infarction.22 However, it is almost impossible to perform routine radionuclide angiography immediately after infarction. Therefore the RVEF obtained with a rapid-response Swan-Ganz catheter system holds promise as a reliable method of quantitatively determining right ventricular systolic function immediately after infarction.
unloading of the left ventricle. In our study the RVEF was not measured before the intraaortic balloon pump was inserted because the pump was inserted immediately after admission. Therefore the change in the RVEF resulting from intraaortic balloon pump insertion is not clear. The intraaortic balloon pump is well known to be effective in improving left ventricular function, but this study suggests a favorable effect of the intraaortic balloon pump on right heart function.
ST elevation in lead V4R and right ventricular dysfunction In our group of patients with stable hemodynamics in whom pressors were not used, the average right atrial pressure, pulmonary arterial pressure, pulmonary arterial wedge pressure, and cardiac index did not differ significantly based on the presence or absence of ST elevation. However, RVEF was lower and right ventricular end-systolic volume index and end-diastolic volume index were higher in patients with ST elevation. This result clearly shows that ST elevation in V4R reflects decreased right ventricular function caused by right ventricular infarction. It is interesting that only ST elevation in V4R was demonstrated by logistic regression analysis to be an independent factor for determining the decline of RVEF.
Effect of intraaortic balloon pump on right ventricular function
Limitations
The RVEF in patients with ST elevation in V4R who required intraaortic balloon pump insertion tended to be higher than in patients who did not require an intraaortic balloon pump. The intraaortic balloon pump may improve right ventricular systolic function by increasing right coronary artery blood flow or by increasing the contribution of contraction of the interventricular septum to right ventricular systole through
In this study the measurement of right heart function was performed after reperfusion therapy was initiated. Therefore these data may not reflect right heart function during right coronary artery occlusion. Although it is possible that the hemodynamics improved rapidly when reperfusion was established, it seems more likely that the right ventricular myocardium was stunned by temporary reduction of right ventricular
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perfusion. Although hemodynamics before reperfusion should be examined, this is impossible to do in human beings for ethical reasons. To address this problem patients in whom reperfusion cannot be performed for various reasons should be studied.
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Background The prognosis of acute inferior myocardial infarction is worse when it is complicated by right ventricular infarction. ST elevation in the right precordial leads is one of the reliable methods for detecting acute right ventricular infarction. The purpose of the study was to examine the relation between ST elevation in the right precordial electrocardiographic leads during acute inferior infarction and the severity of right ventricular systolic dysfunction.
Methods This study analyzed the relation between ST elevation ≥0.1 mV in V4R and the severity of right ventricular systolic dysfunction in 43 consecutive patients (men/women: 35/8; average age 62 ± 9 years) with acute inferior myocardial infarction with a rapid-response Swan-Ganz catheter to measure the right ventricular ejection fraction (RVEF). Results RVEF was significantly lower in patients with ST elevation (n = 18) than in those without (n = 25) (33% ± 6% vs 40% ± 9%, p = 0.010). If the infarct-related lesion was located in the proximal right coronary artery, RVEF tended to be lower than if the lesion was located in the distal right coronary artery or the left circumflex coronary artery (33% ± 10% vs 37% ± 9% vs 42% ± 9%, p = 0.101). Logistic regression analysis demonstrated that ST elevation in V4R was the only independent predictor of depressed RVEF (odds ratio = 5.31, 95% confidence interval = 1.28 to 22.1, p = 0.022).
Conclusion ST elevation in lead V4R during acute inferior myocardial infarction predicts right ventricular systolic dysfunction. (Am Heart J 1998;135:689-95.)
Although right ventricular infarction was first described more than 60 years ago,1 it has not attracted much clinical attention until recently. Corn et al.2 reported in 1974 that hemodynamics deteriorate markedly and atrioventricular block tends to occur in patients with right ventricular infarction, with a resulting increase in the hospital death rate.3,4 Therefore it is critical to determine early whether right ventricular infarction is present and to initiate appropriate therapy as soon as possible. Although the hemodynamic abnormalities of patients with a typical right ventricular infarction are well understood,5 right ventricular function including right-sided hemodynamics immediately after the onset of inferior infarction remains to be understood clearly. The diagnosis of right ventricular infarction can be based on electrocardiographic (ECG) changes,3,6-13 From the Second Department of Internal Medicine, Kyorin University School of Medicine. Submitted Feb. 24, 1997; accepted Jan. 9, 1998. Reprint requests: Kyozo Ishikawa, MD, Second Department of Internal Medicine, Kyorin University School of Medicine, 6-20-2 Shinkawa, Mitaka, Tokyo 181, Japan. Copyright © 1998 by Mosby, Inc. 0002-8703/98/$5.00 + 0 4/1/88734
echocardiography,14-20 radionuclide angiography,21-25 pyrophosphate myocardial scintigraphy,21 or right ventricular catheterization.2,26,27 Of these methods, right precordial ECG leads provide the simplest and most objective data in the acute stage of infarction. However, a method of quantitatively evaluating right ventricular systolic function during acute right ventricular infarction has not yet been developed. Echocardiography and right ventricular angiography are commonly used to evaluate right ventricular systolic dysfunction, but the interpretation of echocardiograms is subjective, and right ventricular angiograms are inappropriate for serial measurement. Furthermore there have been no direct, simultaneous, and quantitative comparisons of the relation between changes in the right precordial ECG leads and right ventricular systolic dysfunction after acute right ventricular infarction. The recently developed rapid-response Swan-Ganz catheter system28-31 enables reproducible measurement of the right ventricular ejection fraction (RVEF).32,33 With this catheter system we determined the relation between right ventricular function and ST elevation in lead V4R during acute inferior myocardial infarction.
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Methods Patients Forty-three consecutive patients (35 men, 61.4 ± 8.6 years of age [mean ± SD], range 41 to 80 years) satisfying the inclusion criteria described in the following text were selected from a series of 56 consecutive patients admitted for a first acute inferior myocardial infarction to the coronary care unit of Kyorin University Hospital within 6 hours after the onset of typical chest pain. The inclusion criteria included (1) age ≤80 years, (2) successful insertion of a modified triple-lumen Swan-Ganz catheter with intracardiac electrodes and a rapidresponse (100 msec) thermistor (model 93A-431H-7.5F, Baxter Healthcare Co., Irvine, Calif.) within 2 hours after arrival in the emergency department, and (3) identification of the infarct-related artery by emergent coronary angiography and achievement of successful reperfusion. This study was done prospectively. Standard 12-lead electrocardiograms and right precordial electrocardiograms (leads V3R through V6R) were recorded immediately after the patient was admitted to the emergency department. Right ventricular infarction was defined by ST-segment elevation ≥0.1 mV in lead V4R. Blood samples for the measurement of creatine phosphokinase activity were collected every 3 hours until a peak value was obtained.
Reperfusion therapy and left heart catheterization The delay between the diagnosis of acute myocardial infarction and reperfusion therapy was generally less than 1 hour. Cardiac catheterization was performed with the Seldinger technique, and coronary angiograms were obtained in multiple views in a routine manner by the Judkins technique. After occlusion (total or subtotal) of the vessel supplying the infarct zone was confirmed, emergency primary percutaneous transluminal coronary angioplasty (PTCA) or coronary thrombolysis with tissue-plasminogen activator (alteplase) administered through a selective coronary catheter was performed. In six patients coronary thrombolysis with intravenous infusion of tissue-plasminogen activator was performed. In these patients the infarct-related lesions were confirmed by emergency coronary angiography at the end of reperfusion therapy. Patients with unsuccessful thrombolysis (Thrombolysis in Myocardial Infarction flow34 grade 0 to 1) underwent rescue PTCA. Successful reperfusion was defined as an improvement in coronary flow to Thrombolysis in Myocardial Infarction grade 2 or 3 flow. In seven patients the coronary blood flow was Thrombolysis in Myocardial Infarction flow grade 2 or better at the time of initial coronary angiography. In these patients coronary angiography was terminated without reperfusion therapy. Written informed consent was obtained from each patient after the risks and potential complications of cardiac catheterization and reperfusion therapy were explained appropriately. Among the 39 patients who did not require an intraaortic balloon pump, 11 patients achieved reperfusion with tissue-plasminogen activator and had an RVEF of 36.5% ± 7.5%, whereas 21
patients underwent PTCA and had an RVEF of 36.0% ± 8.1%. Seven patients who had spontaneous coronary reflow without reperfusion therapy had an RVEF of 38.6% ± 12.7%.
Measurement of right heart hemodynamics and right ventricular ejection fraction Right heart catheterization was performed through the right femoral vein immediately after coronary reperfusion therapy at the catheterization laboratory. A modified triplelumen Swan-Ganz catheter32,33 with intracardiac electrodes and a rapid-response thermistor was advanced until the tip was in the pulmonary artery. The pressure from the proximal lumen was monitored to ensure that the proximal port of the catheter was in the right atrium. The right atrial pressure, pulmonary arterial pressure, and pulmonary capillary wedge pressure were monitored. To determine right ventricular volumes, a rapid manual injection of 5 ml cold saline solution (1° C to 5° C) was performed through the proximal port. Data from the thermodilution curves were processed by a computer system (American Edwards Laboratory, Santa Ana, Calif.) together with an electrocardiographic signal for the determination of heart rate, cardiac output, right ventricular end-diastolic volume index, right ventricular end-systolic volume index, stroke volume index, and RVEF.
Logistic regression analysis Seven clinical variables were used for multivariate logistic regression models to identify correlates of the binary response variable (RVEF <35%). The variables examined included right atrial pressure, systolic pulmonary pressure, ST elevation in lead V4R, use of reperfusion therapy, use of intravenous pressor therapy, residual stenosis in the infarctrelated artery, and location of the infarct-related lesion.
Statistical analysis Statistical analysis was performed with StatView 4.11. Logistic regression was done with “LOGISTIC REGRESSION” from SPSS for Macintosh (Version 6.1J). Data are expressed as the mean ± SD. Comparisons between two groups were performed with the unpaired Student’s t test. Statistically significant differences among three groups were determined by one-way analysis of variance (ANOVA) followed by Bonferroni’s procedure if the ANOVA probability value was <0.05. A chi-squared test was used for comparison of categoric data. Results were considered statistically significant if p < 0.05. The odds ratios, 95% confidence intervals, and p values of the final model (i.e., after adjustment for all other significant covariates) are reported.
Results ST elevation in lead V4R and clinical characteristics The ST elevation and non-ST elevation groups did not differ significantly in terms of baseline clinical
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characteristics (Table I) except for the heart rate (p = 0.004), cardiac index (p = 0.024), and peak creatine phosphokinase activity (p = 0.046). All of the patients in the ST elevation group received acute reperfusion therapy (angioplasty or thrombolytic therapy), whereas seven (28%) patients in the non-ST elevation group received no reperfusion therapy because they had confirmed reflow at the time of emergency coronary angiography (p = 0.046).
ST elevation in lead V4R and right ventricular dysfunction The RVEF was significantly lower and the right ventricular end-systolic volume index was significantly greater in the ST elevation group than in the non-ST elevation group (Table I). However, the right ventricular end-diastolic volume index did not differ significantly between the two groups. No other significant differences were seen in hemodynamic indexes between the two groups except heart rate and cardiac index. Pressors such as dopamine and dobutamine were given to 8 (44%) of 18 patients in the ST elevation group and to 6 (24%) of 25 patients in the non-ST elevation group. Right ventricular function without the effect of pressors was compared between the two groups after patients who received pressors were excluded (Table II). The ST-elevation group (n = 10) had a lower RVEF (p < 0.001), a higher right ventricular end-diastolic volume index (p = 0.025), and a higher right ventricular end-systolic volume index (p = 0.006) compared with the non-ST elevation group (n = 19). No other significant differences were found in all hemodynamic indexes between the two groups. An intraaortic balloon pump was used in 3 (17%) of the 18 patients in the ST elevation group and 1 (4%) of the 25 patients in the non-ST elevation group to augment blood pressure. In the ST-elevation group the RVEF of the 3 patients requiring intraaortic balloon pump insertion tended to be higher than in the 15 patients who did not require an intraaortic balloon pump (38.7% ± 3.8% vs 31.9% ± 5.8%). Therefore those patients requiring an intraaortic balloon pump were excluded, and right ventricular function was compared between the ST elevation group (n = 15) and the non-ST elevation group (n = 24). Significant differences were noted between the ST elevation group and the non-ST elevation group with respect to RVEF (31.9% ± 5.8% vs 39.5% ± 9.0%, p = 0.006), right ventricular end-systolic volume index (87 ± 41 ml/m2 vs 65 ± 23 ml/m2, p = 0.036), heart rate (88.7 ± 18.1
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Table I. Clinical and hemodynamic characteristics of patients with or without ST-segment elevation in lead V4R ST elevation (+) (n = 18) Male/female Age (yr) Risk factors Smoking (%) Hypertension (%) Diabetes mellitus (%) Hyperlipidemia (%) Additional therapy DOA/DOB (%) IABP (%) Reperfusion therapy (%) PTCA tPA Conservative Infarct-related artery (%) RCA proximal RCA distal LCx Coronary stenosis (% stenosis) Before reperfusion No. of diseased vessels (%) One Two Three Combined with LAD lesion (%) Peak CPK (IU/L) Right ventricular function RVEF (%) RVESVI (ml/m2) RVEDVI (ml/m2) RVSVI (ml/m2) Hemodynamic parameters BP systole (mm Hg) Heart rate (beats/min) RAP (mm Hg) PAP systole (mm Hg) PAP diastole (mm Hg) PCWP (mm Hg) CI (L/min/m2)
ST elevation (-) p (n = 25) Value
13/5 60.3 ± 8.4
22/3 62.3 ± 8.7
NS NS
72 61 44 33
70 61 17 26
NS NS NS NS
44 17
24 4
NS NS 0.046
67 33 0
52 20 28
50 44 6
36 44 20
98.4 ± 3.3
99.5 ± 0.5
NS
NS NS
56 33 11 22 4670 ± 3428
60 16 24 32 NS 2313 ± 1649 0.005
33.1 ± 6.0 85.1 ± 37.6 122.7 ± 42.1 38.7 ± 8.6
39.6 ± 8.8 0.010 65.7 ± 22.9 0.042 104.7 ± 25.4 NS 39.2 ± 8.5 NS
123 ± 16 91.5 ± 17.7 6.1 ± 2.8 22.6 ± 4.9 12.9 ± 3.9 11.4 ± 3.5 3.47 ± 0.91
127 ± 9 NS 77.8 ± 11.7 0.004 6.7 ± 4.2 NS 21.5 ± 5.1 NS 12.5 ± 3.6 NS 10.0 ± 4.0 NS 2.95 ± 0.54 0.024
NS, Not significant; DOA/DOB, dopamine and/or dobutamine; IABP, intraaortic balloon pump; RCA proximal, proximal segment of right coronary artery; RCA distal, distal segment of right coronary artery; LCx, left circumflex coronary artery; LAD, left anterior descending coronary artery; CPK, creatine phosphokinase; RVESVI, right ventricular endsystolic volume index; RVEDVI, right ventricular end-diastolic volume index; RVSVI, right ventricular stroke volume index; BP systole, systolic blood pressure; RAP, right atrial pressure; PAP systole, systolic pulmonary arterial pressure; PAP diastole, diastolic pulmonary arterial pressure; PCWP, pulmonary capillary wedge pressure; CI, cardiac index.
beats/min vs 77.8 ± 12.0 beats/min, p = 0.028), and peak creatine phosphokinase activity (4130 ± 3472 IU/L vs 2343 ± 1677 IU/L, p = 0.037).
Infarct-related lesion and right ventricular function The RVEF was lower and the right ventricular enddiastolic volume index and right ventricular end-sys-
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Table II. Hemodynamic characteristics of patients who did not require infusion of dopamine or dobutamine
RVEF (%) RVEDVI (ml/m2) RVESVI (ml/m2) BP systole (mm Hg) Heart rate (beats/min) RAP (mm Hg) PAP systole (mm Hg) PAP diastole (mm Hg) PCWP (mm Hg) Cardiac index (ml/m2)
ST elevation (+) (n = 10)
ST elevation (-) (n = 19)
31.0 ± 6.7 133.9 ± 53.9 95.5 ± 47.8 126.6. ± 15.9 81.7 ± 11.6 5.4 ± 2.2 22.2 ± 5.4 11.0 ± 2.5 11.9 ± 4.4 3.06 ± 0.86
41.4 ± 6.7 98.2 ± 22.8 59.1 ± 17.8 128.2 ± 9.5 77.2 ± 12.7 6.1 ± 4.0 21.8 ± 5.5 12.2 ± 3.8 9.8 ± 3.8 2.92 ± 0.48
p Value <0.001 0.025 0.006 NS NS NS NS NS NS NS
NS, Not significant; DOA/DOB, infusion of dopamine and/or dobutamine; RVEDVI, right ventricular end-diastolic volume index; RVESVI, right ventricular end-systolic volume index; BP systole, systolic blood pressure; RAP, right atrial pressure; PAP systole, systolic pulmonary arterial pressure; PAP diastole, diastolic pulmonary arterial pressure; PCWP, pulmonary capillary wedge pressure.
tolic volume index tended to be greater, although not significantly, when the lesion was in the proximal portion of the right coronary artery (n = 17) compared with lesions in the distal right coronary artery (n = 19) or in the left circumflex coronary artery (n = 7) (Table III). No difference in RVEF was noted with respect to the method of reperfusion (angioplasty vs thrombolysis vs spontaneous reflow, 36.0% ± 8.1% vs 36.5% ± 7.5% vs 38.6% ± 12.7%, respectively).
Logistic regression analysis The factors associated with a lower RVEF were examined by logistic regression analysis. Only ST elevation in V4R was significantly associated with an RVEF <35% (odds ratio = 5.31, 95% confidence interval = 1.28 to 22.1, p = 0.022).
Discussion At present no method exists for evaluating right ventricular systolic function quantitatively in patients with acute myocardial infarction. However, rapidresponse Swan-Ganz catheter systems allow for the continuous measurement of RVEF, which can be used as an indicator of right ventricular systolic function during acute myocardial infarction.32,33 Analysis of the relation between the RVEF obtained by this method and ST elevation in V4R in this study demonstrates that the RVEF was significantly lower in patients with ST elevation.
Right ventricular infarction The prognosis worsens and the morbidity rate increases for patients with inferior myocardial infarc-
tion when right ventricular infarction is also present during the acute stage.36 According to Zehender et al.3,37 the hospital death rate reaches 30% or more in patients with an inferior myocardial infarction complicated by right ventricular infarction that is not treated with reperfusion therapy. Even in the setting of mild left ventricular systolic dysfunction, these patients tend to have hemodynamic abnormalities and have shock at a high frequency.4 Right ventricular infarction is diagnosed by ST elevation in leads V3R or V4R5,10-13 and by the evidence of right ventricular enlargement,14 abnormal right ventricular wall motion, and paradoxical movement of the interventricular septum15-18 on two-dimensional echocardiography or increased right heart filling pressure determined by right heart catheterization.2,26,27 The diagnosis of right ventricular infarction in the subacute stage is primarily based on the detection of right ventricular systolic dysfunction on radionuclide angiography.7,22,23,25 During the very acute stage of infarction, ST elevation in lead V4R is considered to be superior with respect to diagnostic accuracy and simplicity.4,8,11
Evaluation of right ventricular function Echocardiography and right ventricular contrast angiography are generally used to evaluate right ventricular systolic function. However, echocardiography has a limited capability to evaluate right ventricular systolic function quantitatively, although it is useful for assessing the hemodynamic abnormalities that accompany right ventricular infarction. In addition, right ventricular angiography is not suitable for serial evaluation
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Table III. Location of the infarct-related lesion and right ventricular function
RVEF (%) RVEDVI (ml/m2) RVESVI (ml/m2) Cardiac index (L/min/m2)
Prox RCA (n = 17)
Dist RCA (n = 19)
LCx (n = 7)
32.7 ± 10.0 140.3 ± 99.7 102.4 ± 99.6 3.26 ± 0.94
37.2 ± 8.9 108.7 ± 39.6 71.6 ± 37.6 2.96 ± 0.69
41.6 ± 9.2 106.0 ± 21.2 64.7 ± 17.7 3.33 ± 0.42
p Value NS NS NS NS
NS, Not significant; Prox RCA, patients with proximal right coronary artery lesions; Dist RCA, patients with distal right coronary artery lesions; LCx, patients with left circumflex coronary artery lesions; RVEDVI, right ventricular end-diastolic volume index; RVESVI, right ventricular end-systolic volume index.
of right ventricular systolic function. Elevation of the right ventricular filling pressure, that is, an increase in the mean right atrial pressure, is an important criterion for the diagnosis of right ventricular infarction. However, the diagnostic accuracy of this factor is limited because the mean right atrial pressure quickly falls if fluid replacement is insufficient or if diuretics are used. Furthermore this study demonstrated that even in patients with ST elevation and a reduced RVEF, which are clear indications of right ventricular systolic dysfunction, increased right atrial pressure was rarely observed. A right atrial pressure ≥10 mm Hg was noted in 1 (6%) of the 18 patients in the ST elevation group and in 5 (20%) of the 25 patients in the non-ST elevation group. Previous studies22,23 have suggested that radionuclide angiography is the gold standard for the evaluation of right heart function, because it allows for the analysis of right ventricular systolic abnormalities by phase analysis in patients with right ventricular infarction.22 However, it is almost impossible to perform routine radionuclide angiography immediately after infarction. Therefore the RVEF obtained with a rapid-response Swan-Ganz catheter system holds promise as a reliable method of quantitatively determining right ventricular systolic function immediately after infarction.
unloading of the left ventricle. In our study the RVEF was not measured before the intraaortic balloon pump was inserted because the pump was inserted immediately after admission. Therefore the change in the RVEF resulting from intraaortic balloon pump insertion is not clear. The intraaortic balloon pump is well known to be effective in improving left ventricular function, but this study suggests a favorable effect of the intraaortic balloon pump on right heart function.
ST elevation in lead V4R and right ventricular dysfunction In our group of patients with stable hemodynamics in whom pressors were not used, the average right atrial pressure, pulmonary arterial pressure, pulmonary arterial wedge pressure, and cardiac index did not differ significantly based on the presence or absence of ST elevation. However, RVEF was lower and right ventricular end-systolic volume index and end-diastolic volume index were higher in patients with ST elevation. This result clearly shows that ST elevation in V4R reflects decreased right ventricular function caused by right ventricular infarction. It is interesting that only ST elevation in V4R was demonstrated by logistic regression analysis to be an independent factor for determining the decline of RVEF.
Effect of intraaortic balloon pump on right ventricular function
Limitations
The RVEF in patients with ST elevation in V4R who required intraaortic balloon pump insertion tended to be higher than in patients who did not require an intraaortic balloon pump. The intraaortic balloon pump may improve right ventricular systolic function by increasing right coronary artery blood flow or by increasing the contribution of contraction of the interventricular septum to right ventricular systole through
In this study the measurement of right heart function was performed after reperfusion therapy was initiated. Therefore these data may not reflect right heart function during right coronary artery occlusion. Although it is possible that the hemodynamics improved rapidly when reperfusion was established, it seems more likely that the right ventricular myocardium was stunned by temporary reduction of right ventricular
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perfusion. Although hemodynamics before reperfusion should be examined, this is impossible to do in human beings for ethical reasons. To address this problem patients in whom reperfusion cannot be performed for various reasons should be studied.
18.
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