- Email: [email protected]
Stress echocardiography and exercise electrocardiography for risk stratification after non–Q-wave uncomplicated myocardial infarction
Stress Echocardiography and Exercise Electrocardiography for Risk Stratification After Non–Q-Wave Uncomplicated Myocardial Infarction Alessandro Desideri, MD, Riccardo Bigi, MD, Gian Leone Suzzi, MD, Claudio Coletta, MD, Dario Gregori, MA, PhD, Gino Valente, MD, and Paolo Fioretti, MD, PhD isk stratification after acute myocardial infarction (AMI) is a major challenge for the cardiologist. R Many studies have analyzed the relative value of noninvasive tests in identifying patients at risk for future events after uncomplicated Q-wave AMI. However, the predictive value of noninvasive tests in the setting of non–Q-wave AMI remains to be determined. We performed a prospective study to determine the relative value of exercise electrocardiography (ECG) and pharmacologic stress echocardiography in risk stratification after uncomplicated non–Q-wave AMI. •••
Sixty-eight patients with non–Q-wave infarction were selected from 348 consecutive survivors of AMI. All patients underwent maximum symptom-limited exercise ECG and stress echocardiography within 15 days of hospital admission on different days and in random order after 48 hours of pharmacologic washout. Exercise ECG was performed by means of an electromagnetically braked, upright bicycle ergometer test with 25-W incremental loading every 2 minutes. A positive test was defined by the appearance of ⬎1 mm horizontal or downsloping ST-segment depression at 0.08 second after the J point, with or without chest pain. Test end points were achievement of maximal age-related heart rate, limiting symptoms, typical chest pain, ST-segment depression ⬎3 mm, a decrease in blood pressure, or appearance of complex arrhythmias. Two-dimensional echocardiography was performed on day 9 ⫾ 4, in therapy, at rest, and in combination with pharmacologic stress with either dipyridamole or dobutamine. Two-dimensional echocardiography was performed using Hewlett-Packard Sonos 2500 (Palo Alto, California) or Acuson XP-10 (Mountain View, California) imaging systems. Images were stored on videotape and subsequently analyzed with resting and stress recordings side by side by 2 expert cardiologists who were blinded to the exercise electrocardiographic result. Dipyridamole was infused at a dose of 0.56 mg/kg over 4 minutes followed by 4 minutes of no dose. and if negative, by a second dose of 0.28 mg/kg in 2 minutes, with a cumulative dose of 0.84 mg/kg over 10 minutes. The From the Department of Cardiology, “S. Giacomo” Hospital, Castelfranco Veneto; Department of Cardiology; “E. Morelli Hospital”, Sondalo; Department of Cardiology, “S. Spirito” Hospital, Rome; Department of Cardiology, “IRCAB” Research Foundation, Udine; and Department of Cardiology, “S. Maria della Misericordia” Hospital, Udine, Italy. Dr. Desideri’s address is: Cardiology Dept, S. Giacomo Hospital, 31033 Castelfranco Veneto, Italy. E-mail: [email protected]. Manuscript received March 1, 1999; revised manuscript received and accepted May 3, 1999. ©1999 by Excerpta Medica, Inc. All rights reserved. The American Journal of Cardiology Vol. 84 September 15, 1999
test was interrupted by aminophilline after 15 minutes for the negative tests or when clear asynergy appeared (70 to 240 mg in 1 to 3 minutes). Dobutamine was infused in 3-minute dose increments, starting from 5 g/kg/min and increasing to 10, 20, 30, and 40 g/ kg/min. Additional atropine, up to 1 mg, was added if necessary to achieve the target heart rate. Infusion was immediately discontinued as soon as criteria for positivity were reached during the test. The use of either dipyridamole or dobutamine as a pharmacologic stressor depended upon the choice of the cardiologist performing the examination. A positive test result was defined as the appearance of a transient ventricular dyssynergy, which was absent or of a lesser degree at baseline examination, and was regarded as a discontinuation criterion. The test was also halted in cases of peak drug dose, achievement of conventional nonechocardiographic “ischemic” end points (severe chest pain and/or ST-segment shift ⬎0.2 mV), intolerable symptoms, and limiting asymptomatic side effects such as hypertension (systolic blood pressure ⬎220 mm Hg, diastolic blood pressure ⬎120 mm Hg), hypotension (30 mm Hg decrease in blood pressure), and complex arrhythmias. Two-dimensional echocardiographic monitoring was performed throughout drug infusion and up to 5 minutes thereafter. The left ventricular wall was divided into 16 segments whose motion was scored as follows: 1 ⫽ normal, 2 ⫽ hypokinetic, 3 ⫽ akinetic, and 4 ⫽ dyskinetic. Rest and peak wall motion score index were derived by the summation of the individual segment score divided by the number of segment interpreted. Akinesia at rest that became dyskinesia during stress was not taken into account. The ejection fraction was calculated on a single plane according to the area-length method. Planimetry of end-systolic and end-diastolic areas was performed by manual tracing of the endocardial border. All patients were prospectively followed up for a mean of 284 days (range 155 to 610). Spontaneous cardiac events were defined as death from cardiac causes, nonfatal myocardial reinfarction, and unstable angina requiring hospitalization. Only the first event was taken into account for each patient. Patients were referred for coronary angiography at the discretion of the staff cardiologist. The decision to perform revascularization procedures was made by the cardiologist, who was blinded to the study goals. Revascularization was not considered an end point and all subjects undergoing revascularization were censored at the time of procedure. 0002-9149/99/$–see front matter PII S0002-9149(99)00425-7
739
FIGURE 1. Kaplan-Meier analysis of event-free survival related to time from study entry for exercise ECG and stress echocardiography.
Continuous variables were expressed as mean ⫾ 1 SD and were compared using the t test. The 95% confidence interval (CI) is reported where appropriate. Proportions were compared by means of chi-square statistics. Multivariate stepwise analysis with the Cox model (SAS statistical software, SAS Institute, Cary, North Carolina) was used to assess the outcome predictors. Clinical (age, gender, prior myocardial infarction, thrombolytic therapy, peak creatine kinase), exercise ECG, (positive exercise electrocardiogram, chest pain during exercise, peak heart rate achieved), and echocardiographic (positive stress echo, ejection fraction, resting and peak wall motion score index) variables were tested. Kaplan-Meier curves and logrank test were used to describe event-free survival related to time from study entry. A p value ⬍0.05 was considered to be statistically significant. A positive exercise electrocardiogram was found in 29 patients (43%), 11 of whom complained of typical chest pain during the test. New wall motion abnormalities during stress echocardiography were observed in 36 patients (53%). Resting and peak wall motion score index were 1.25 (95% CI 1.1 to 1.4) and 1.37 (95% CI 1.2 to 1.6), respectively. Twenty-eight spontaneous events (1 cardiac death, 5 AMIs, and 22 unstable angina, followed by angioplasty in 11 cases and bypass surgery procedures in 9 cases) occurred during follow-up. Thus, the total event rate was 41% (28 of 68). Univariate analysis selected a positive exercise electrocardiogram (likelihood ratio 10.2, p ⫽ 0.004) and a positive stress echocardiogram (likelihood ratio 7.9, p ⫽ 0.01) as predictors of events. Multivariate analysis identified positive stress echocardiograhy (p ⫽ 0.03) and positive exercise ECG (p 740 THE AMERICAN JOURNAL OF CARDIOLOGY姞
VOL. 84
⫽ 0.04) as independent predictors of events. KaplanMeier curves of event-free survival related to time from study entry are presented in Figure 1. •••
Predischarge evaluation is usually aimed at identifying high-risk patients following AMI. In patients with uncomplicated AMI, different stratification modalities have been proposed. Exercise ECG is still the most commonly used method because it is simple and easily available. More recently, we and others showed that dipyridamole stress echocardiography can provide independent information compared with clinical and exercise electrocardiographic data in this group of patients.1– 4 Nevertheless, no definitive data are currently available on the direct comparison of these 2 techniques in the same patient population after uncomplicated non–Q-wave AMI. This issue seems particularly important because recent studies suggest that the aggressive approach to patients recovering from unstable angina or non–Q-wave AMI is not rewarding compared with a conservative strategy.5–7 Available data do not support the routine use of exercise ECG before hospital discharge.8 Even the current limited information on the prognostic value of stress echocardiography in non–Q-wave post-AMI patients seems contradictory. Some investigators have referred high specificity of stress echocardiography,9 whereas caution in the use of this test for risk stratification in this subset of patients has been suggested by others.10 A recent paper investigated the role of dobutamine echocardiography in predicting future spontaneous events in patients with Q-wave or non–Q-wave AMI.11 Results showed that positive stress echocardiography is a powerful predictor of future spontaneous events. Our SEPTEMBER 15, 1999
data confirm the capability of stress echocardiography to identify spontaneous events in a patient population that also performed exercise testing. The choice of the stressor was left to the cardiologist performing the test. No stressor confounding factor was seen anywhere, which is consistent with the results of other studies that show similar prognostic value of the 2 stressors. This study suggests that stress echocardiography and exercise ECG have similar predictive value in a patient population recovering from an uncomplicated non–Q-wave AMI and provide important information in identifying patients at risk for subsequent events. 1. Bigi R, Galati A, Curti G, Coletta C, Barlera S, Partesana N, Bordi L, Ceci V,
Occhi G, Fiorentini C. Prognostic value of residual ischaemia assessed by exercise electrocardiography and dobutamine stress echocardiography in low-risk patients following acute myocardial infarction. Eur Heart J 1997;18:1873–1881. 2. Greco C, Salustri A, Seccareccia F, Ciavatti M, Biferali F, Valtorta C, Guzzardi G, Falcone M, Palmarara A. Prognostic value of dobutamine echocardiography early after uncomplicated acute myocardial infarction: a comparison with exercise electrocardiography. J Am Coll Cardiol 1997;29:261–267. 3. Picano E, Landi P, Bolognese L, Chiaranda’ G, Chiarella F, Seveso G, Sclavo MG, Gandolfo N, Previtali M, Orlandini A, Margaria F, Pirelli S, Magaja O, Minardi G, Bianchi F, Marini C, Raciti M, Michelassi C, Severi S, for the EPIC Study Group. Prognostic value of dipyridamole echocardiography early after
uncomplicated myocardial infarction: a large scale, multicenter trial. Am J Med 1993;6:608 – 618. 4. Desideri A, Suzzi GL, Terlizzi R, Canel F, Cernetti C, Celegon L. Dipyridamole stress echocardiography and exercise testing for risk stratification after uncomplicated myocardial infarction. G Ital Cardiol 1998;28:754 –759. 5. Boden W, O’Rourke R, Crawford M, Blaustein A, Deedwania PC, Zoble R, Wexler L, Kleiger R, Pepine C, Ferry D, Chow B, Lavori P, for the Veterans Affairs Non Q Infarction Strategies in Hospital (VANQWISH) Trial Investigators. Outcomes in patients with acute non-q-wave myocardial infarction randomly assigned to an invasive as compared with a conservative management strategy. N Engl J Med 1998;338:1785–1792. 6. Anderson HV, Cannon CP, Stone PH. One year results of the thrombolysis in myocardial (TIMI) IIIB clinical trial. J Am Coll Cardiol 1995;26:1643–1650. 7. Yusuf S, Flather M, Pogue J, Hunt D, Varigos J, Piegas L, Avezum A, Anderson J, Keltai M, Budaj A, Fox K, Ceremuzynsi L, for the OASIS (Organisation to Assess Startegies for Ischaemic Syndromes) Registry Investigators. Variations between countries in invasive cardiac procedures and outcomes in patients with suspected unstable angina or myocardial infarction without initial ST elevation. Lancet 1998;352:507–514. 8. Krone RJ, Dwyer EM, Greenberg H, Miller JP, Gillespie JA. Risk stratification in patients with first non-Q wave infarction: limited value of the early low level exercise test after uncomplicated infarcts. The Multicenter Post-Infarction Research Group. J Am Coll Cardiol 1989;14:31–37. 9. Fiorini G, Prina L, de Ponti C. Prognostic meaning of the echo-dipyridamole test in recent non-Q myocardial infarct. G Ital Cardiol 1989;19:207–212. 10. Lanzarini L, Cavallotti C, Poli A, Fetiveau R, Previtali M, Montemartini C. Results and prognostic significance of echocardiography-dobutamine⫹atropine test in recent non-Q wave myocardial infarction. G Ital Cardiol 1996;26:261– 272. 11. Wang C, Wen-Jin C, Chung-Ching H, Ming-Jui H. Prognostic value of dobutamine echocardiography in patients after Q-wave and non-Q wave acute myocardial infarction. Am J Cardiol 1998;82;38 – 42.
Prognostic Significance of Oxygen Uptake Kinetics During Low Level Exercise in Patients With Heart Failure Hans Peter Brunner-La Rocca, MD, Daniel Weilenmann, MD, Christoph Schalcher, Maria Schlumpf, RN, Ferenc Follath, MD, Reto Candinas, MD, and Wolfgang Kiowski, MD eak oxygen consumption (VO ) reflects the severity of congestive heart failure (CHF) and is P widely accepted as a good prognostic marker. How2
1,2
ever, there is increasing interest in obtaining submaximal exercise testing because of several reasons. First, peak VO2 is not necessarily a reliable parameter of cardiovascular capacity because patient motivation and conditions other than cardiopulmonary diseases may influence it.3 In addition, it has been recently shown in patients early after myocardial infarction with impaired ejection fraction that the increase in cardiac output at exercise onset may be delayed while the maximal cardiac output is still normal.4 Finally, patients hardly perform maximal exercise during daily life. Accordingly, submaximal exercise testing has been increasingly used to assess functional capacity of patients with CHF.5–7 Parameters not requiring maximal From the Department of Internal Medicine, Division of Cardiology, University Hospital, Zurich, Switzerland. Dr. Brunner-La Rocca’s address is: Baker Medical Research Institute, PO Box 6492, St. Kilda Road Central, Melbourne 8008, Victoria, Australia. E-mail: [email protected]. Manuscript received January 22, 1999; revised manuscript received and accepted May 4, 1999. ©1999 by Excerpta Medica, Inc. All rights reserved. The American Journal of Cardiology Vol. 84 September 15, 1999
MD,
exercise (e.g., 6-minute walking distance, ventilation/ carbon dioxide [CO2] output slope) may predict morbidity and mortality in these patients.7,8 Although kinetics of VO2 at exercise onset are altered in patients with CHF,4,9 their prognostic value has not yet been determined. Thus, we sought to prospectively investigate whether VO2 kinetics may be useful for the prognostic assessment of patients with chronic CHF compared with a variety of previously described predictors of prognosis.2,10,11 •••
Forty-eight patients (44 men and 4 women) with ejection fraction ⱖ40% secondary to coronary artery disease in 26 (54%), dilated cardiomyopathy in 18 (38%), and valvular heart disease in 4 (8%), who were in stable condition for at least 3 months, were enrolled from January to December 1996. All patients were taking angiotensin-converting enzyme inhibitors and diuretics, 28 were on digitalis and 22 on amiodarone, and none was on a  blocker. Thirteen patients (27%) had an implantable cardioverter defibrillator, which did not influence results of the study. Patients were excluded if their exercise capacity was limited by reasons other than CHF and if they were on the 0002-9149/99/$–see front matter PII S0002-9149(99)00426-9
741
Sixty-eight patients with non–Q-wave infarction were selected from 348 consecutive survivors of AMI. All patients underwent maximum symptom-limited exercise ECG and stress echocardiography within 15 days of hospital admission on different days and in random order after 48 hours of pharmacologic washout. Exercise ECG was performed by means of an electromagnetically braked, upright bicycle ergometer test with 25-W incremental loading every 2 minutes. A positive test was defined by the appearance of ⬎1 mm horizontal or downsloping ST-segment depression at 0.08 second after the J point, with or without chest pain. Test end points were achievement of maximal age-related heart rate, limiting symptoms, typical chest pain, ST-segment depression ⬎3 mm, a decrease in blood pressure, or appearance of complex arrhythmias. Two-dimensional echocardiography was performed on day 9 ⫾ 4, in therapy, at rest, and in combination with pharmacologic stress with either dipyridamole or dobutamine. Two-dimensional echocardiography was performed using Hewlett-Packard Sonos 2500 (Palo Alto, California) or Acuson XP-10 (Mountain View, California) imaging systems. Images were stored on videotape and subsequently analyzed with resting and stress recordings side by side by 2 expert cardiologists who were blinded to the exercise electrocardiographic result. Dipyridamole was infused at a dose of 0.56 mg/kg over 4 minutes followed by 4 minutes of no dose. and if negative, by a second dose of 0.28 mg/kg in 2 minutes, with a cumulative dose of 0.84 mg/kg over 10 minutes. The From the Department of Cardiology, “S. Giacomo” Hospital, Castelfranco Veneto; Department of Cardiology; “E. Morelli Hospital”, Sondalo; Department of Cardiology, “S. Spirito” Hospital, Rome; Department of Cardiology, “IRCAB” Research Foundation, Udine; and Department of Cardiology, “S. Maria della Misericordia” Hospital, Udine, Italy. Dr. Desideri’s address is: Cardiology Dept, S. Giacomo Hospital, 31033 Castelfranco Veneto, Italy. E-mail: [email protected]. Manuscript received March 1, 1999; revised manuscript received and accepted May 3, 1999. ©1999 by Excerpta Medica, Inc. All rights reserved. The American Journal of Cardiology Vol. 84 September 15, 1999
test was interrupted by aminophilline after 15 minutes for the negative tests or when clear asynergy appeared (70 to 240 mg in 1 to 3 minutes). Dobutamine was infused in 3-minute dose increments, starting from 5 g/kg/min and increasing to 10, 20, 30, and 40 g/ kg/min. Additional atropine, up to 1 mg, was added if necessary to achieve the target heart rate. Infusion was immediately discontinued as soon as criteria for positivity were reached during the test. The use of either dipyridamole or dobutamine as a pharmacologic stressor depended upon the choice of the cardiologist performing the examination. A positive test result was defined as the appearance of a transient ventricular dyssynergy, which was absent or of a lesser degree at baseline examination, and was regarded as a discontinuation criterion. The test was also halted in cases of peak drug dose, achievement of conventional nonechocardiographic “ischemic” end points (severe chest pain and/or ST-segment shift ⬎0.2 mV), intolerable symptoms, and limiting asymptomatic side effects such as hypertension (systolic blood pressure ⬎220 mm Hg, diastolic blood pressure ⬎120 mm Hg), hypotension (30 mm Hg decrease in blood pressure), and complex arrhythmias. Two-dimensional echocardiographic monitoring was performed throughout drug infusion and up to 5 minutes thereafter. The left ventricular wall was divided into 16 segments whose motion was scored as follows: 1 ⫽ normal, 2 ⫽ hypokinetic, 3 ⫽ akinetic, and 4 ⫽ dyskinetic. Rest and peak wall motion score index were derived by the summation of the individual segment score divided by the number of segment interpreted. Akinesia at rest that became dyskinesia during stress was not taken into account. The ejection fraction was calculated on a single plane according to the area-length method. Planimetry of end-systolic and end-diastolic areas was performed by manual tracing of the endocardial border. All patients were prospectively followed up for a mean of 284 days (range 155 to 610). Spontaneous cardiac events were defined as death from cardiac causes, nonfatal myocardial reinfarction, and unstable angina requiring hospitalization. Only the first event was taken into account for each patient. Patients were referred for coronary angiography at the discretion of the staff cardiologist. The decision to perform revascularization procedures was made by the cardiologist, who was blinded to the study goals. Revascularization was not considered an end point and all subjects undergoing revascularization were censored at the time of procedure. 0002-9149/99/$–see front matter PII S0002-9149(99)00425-7
739
FIGURE 1. Kaplan-Meier analysis of event-free survival related to time from study entry for exercise ECG and stress echocardiography.
Continuous variables were expressed as mean ⫾ 1 SD and were compared using the t test. The 95% confidence interval (CI) is reported where appropriate. Proportions were compared by means of chi-square statistics. Multivariate stepwise analysis with the Cox model (SAS statistical software, SAS Institute, Cary, North Carolina) was used to assess the outcome predictors. Clinical (age, gender, prior myocardial infarction, thrombolytic therapy, peak creatine kinase), exercise ECG, (positive exercise electrocardiogram, chest pain during exercise, peak heart rate achieved), and echocardiographic (positive stress echo, ejection fraction, resting and peak wall motion score index) variables were tested. Kaplan-Meier curves and logrank test were used to describe event-free survival related to time from study entry. A p value ⬍0.05 was considered to be statistically significant. A positive exercise electrocardiogram was found in 29 patients (43%), 11 of whom complained of typical chest pain during the test. New wall motion abnormalities during stress echocardiography were observed in 36 patients (53%). Resting and peak wall motion score index were 1.25 (95% CI 1.1 to 1.4) and 1.37 (95% CI 1.2 to 1.6), respectively. Twenty-eight spontaneous events (1 cardiac death, 5 AMIs, and 22 unstable angina, followed by angioplasty in 11 cases and bypass surgery procedures in 9 cases) occurred during follow-up. Thus, the total event rate was 41% (28 of 68). Univariate analysis selected a positive exercise electrocardiogram (likelihood ratio 10.2, p ⫽ 0.004) and a positive stress echocardiogram (likelihood ratio 7.9, p ⫽ 0.01) as predictors of events. Multivariate analysis identified positive stress echocardiograhy (p ⫽ 0.03) and positive exercise ECG (p 740 THE AMERICAN JOURNAL OF CARDIOLOGY姞
VOL. 84
⫽ 0.04) as independent predictors of events. KaplanMeier curves of event-free survival related to time from study entry are presented in Figure 1. •••
Predischarge evaluation is usually aimed at identifying high-risk patients following AMI. In patients with uncomplicated AMI, different stratification modalities have been proposed. Exercise ECG is still the most commonly used method because it is simple and easily available. More recently, we and others showed that dipyridamole stress echocardiography can provide independent information compared with clinical and exercise electrocardiographic data in this group of patients.1– 4 Nevertheless, no definitive data are currently available on the direct comparison of these 2 techniques in the same patient population after uncomplicated non–Q-wave AMI. This issue seems particularly important because recent studies suggest that the aggressive approach to patients recovering from unstable angina or non–Q-wave AMI is not rewarding compared with a conservative strategy.5–7 Available data do not support the routine use of exercise ECG before hospital discharge.8 Even the current limited information on the prognostic value of stress echocardiography in non–Q-wave post-AMI patients seems contradictory. Some investigators have referred high specificity of stress echocardiography,9 whereas caution in the use of this test for risk stratification in this subset of patients has been suggested by others.10 A recent paper investigated the role of dobutamine echocardiography in predicting future spontaneous events in patients with Q-wave or non–Q-wave AMI.11 Results showed that positive stress echocardiography is a powerful predictor of future spontaneous events. Our SEPTEMBER 15, 1999
data confirm the capability of stress echocardiography to identify spontaneous events in a patient population that also performed exercise testing. The choice of the stressor was left to the cardiologist performing the test. No stressor confounding factor was seen anywhere, which is consistent with the results of other studies that show similar prognostic value of the 2 stressors. This study suggests that stress echocardiography and exercise ECG have similar predictive value in a patient population recovering from an uncomplicated non–Q-wave AMI and provide important information in identifying patients at risk for subsequent events. 1. Bigi R, Galati A, Curti G, Coletta C, Barlera S, Partesana N, Bordi L, Ceci V,
Occhi G, Fiorentini C. Prognostic value of residual ischaemia assessed by exercise electrocardiography and dobutamine stress echocardiography in low-risk patients following acute myocardial infarction. Eur Heart J 1997;18:1873–1881. 2. Greco C, Salustri A, Seccareccia F, Ciavatti M, Biferali F, Valtorta C, Guzzardi G, Falcone M, Palmarara A. Prognostic value of dobutamine echocardiography early after uncomplicated acute myocardial infarction: a comparison with exercise electrocardiography. J Am Coll Cardiol 1997;29:261–267. 3. Picano E, Landi P, Bolognese L, Chiaranda’ G, Chiarella F, Seveso G, Sclavo MG, Gandolfo N, Previtali M, Orlandini A, Margaria F, Pirelli S, Magaja O, Minardi G, Bianchi F, Marini C, Raciti M, Michelassi C, Severi S, for the EPIC Study Group. Prognostic value of dipyridamole echocardiography early after
uncomplicated myocardial infarction: a large scale, multicenter trial. Am J Med 1993;6:608 – 618. 4. Desideri A, Suzzi GL, Terlizzi R, Canel F, Cernetti C, Celegon L. Dipyridamole stress echocardiography and exercise testing for risk stratification after uncomplicated myocardial infarction. G Ital Cardiol 1998;28:754 –759. 5. Boden W, O’Rourke R, Crawford M, Blaustein A, Deedwania PC, Zoble R, Wexler L, Kleiger R, Pepine C, Ferry D, Chow B, Lavori P, for the Veterans Affairs Non Q Infarction Strategies in Hospital (VANQWISH) Trial Investigators. Outcomes in patients with acute non-q-wave myocardial infarction randomly assigned to an invasive as compared with a conservative management strategy. N Engl J Med 1998;338:1785–1792. 6. Anderson HV, Cannon CP, Stone PH. One year results of the thrombolysis in myocardial (TIMI) IIIB clinical trial. J Am Coll Cardiol 1995;26:1643–1650. 7. Yusuf S, Flather M, Pogue J, Hunt D, Varigos J, Piegas L, Avezum A, Anderson J, Keltai M, Budaj A, Fox K, Ceremuzynsi L, for the OASIS (Organisation to Assess Startegies for Ischaemic Syndromes) Registry Investigators. Variations between countries in invasive cardiac procedures and outcomes in patients with suspected unstable angina or myocardial infarction without initial ST elevation. Lancet 1998;352:507–514. 8. Krone RJ, Dwyer EM, Greenberg H, Miller JP, Gillespie JA. Risk stratification in patients with first non-Q wave infarction: limited value of the early low level exercise test after uncomplicated infarcts. The Multicenter Post-Infarction Research Group. J Am Coll Cardiol 1989;14:31–37. 9. Fiorini G, Prina L, de Ponti C. Prognostic meaning of the echo-dipyridamole test in recent non-Q myocardial infarct. G Ital Cardiol 1989;19:207–212. 10. Lanzarini L, Cavallotti C, Poli A, Fetiveau R, Previtali M, Montemartini C. Results and prognostic significance of echocardiography-dobutamine⫹atropine test in recent non-Q wave myocardial infarction. G Ital Cardiol 1996;26:261– 272. 11. Wang C, Wen-Jin C, Chung-Ching H, Ming-Jui H. Prognostic value of dobutamine echocardiography in patients after Q-wave and non-Q wave acute myocardial infarction. Am J Cardiol 1998;82;38 – 42.
Prognostic Significance of Oxygen Uptake Kinetics During Low Level Exercise in Patients With Heart Failure Hans Peter Brunner-La Rocca, MD, Daniel Weilenmann, MD, Christoph Schalcher, Maria Schlumpf, RN, Ferenc Follath, MD, Reto Candinas, MD, and Wolfgang Kiowski, MD eak oxygen consumption (VO ) reflects the severity of congestive heart failure (CHF) and is P widely accepted as a good prognostic marker. How2
1,2
ever, there is increasing interest in obtaining submaximal exercise testing because of several reasons. First, peak VO2 is not necessarily a reliable parameter of cardiovascular capacity because patient motivation and conditions other than cardiopulmonary diseases may influence it.3 In addition, it has been recently shown in patients early after myocardial infarction with impaired ejection fraction that the increase in cardiac output at exercise onset may be delayed while the maximal cardiac output is still normal.4 Finally, patients hardly perform maximal exercise during daily life. Accordingly, submaximal exercise testing has been increasingly used to assess functional capacity of patients with CHF.5–7 Parameters not requiring maximal From the Department of Internal Medicine, Division of Cardiology, University Hospital, Zurich, Switzerland. Dr. Brunner-La Rocca’s address is: Baker Medical Research Institute, PO Box 6492, St. Kilda Road Central, Melbourne 8008, Victoria, Australia. E-mail: [email protected]. Manuscript received January 22, 1999; revised manuscript received and accepted May 4, 1999. ©1999 by Excerpta Medica, Inc. All rights reserved. The American Journal of Cardiology Vol. 84 September 15, 1999
MD,
exercise (e.g., 6-minute walking distance, ventilation/ carbon dioxide [CO2] output slope) may predict morbidity and mortality in these patients.7,8 Although kinetics of VO2 at exercise onset are altered in patients with CHF,4,9 their prognostic value has not yet been determined. Thus, we sought to prospectively investigate whether VO2 kinetics may be useful for the prognostic assessment of patients with chronic CHF compared with a variety of previously described predictors of prognosis.2,10,11 •••
Forty-eight patients (44 men and 4 women) with ejection fraction ⱖ40% secondary to coronary artery disease in 26 (54%), dilated cardiomyopathy in 18 (38%), and valvular heart disease in 4 (8%), who were in stable condition for at least 3 months, were enrolled from January to December 1996. All patients were taking angiotensin-converting enzyme inhibitors and diuretics, 28 were on digitalis and 22 on amiodarone, and none was on a  blocker. Thirteen patients (27%) had an implantable cardioverter defibrillator, which did not influence results of the study. Patients were excluded if their exercise capacity was limited by reasons other than CHF and if they were on the 0002-9149/99/$–see front matter PII S0002-9149(99)00426-9
741