Left ventricular derived cardiac output

Left Ventricular Derived Cardiac Output WILLIAM J. FRENCH, MD, RICHARD J. HASKELL, MD, ROBERT W, KNOUSE, BS, and JOHN MICHAEL CRILEY, MD

Measurement of cardiac output (CO) requires rightsided cardiac catheterization. However, to save time and reduce costs, only left-sided cardiac catheterization is usually performed in most patients with suspected coronary artery disease. Thus, CO is not measured. To determine if CO can be measured from the left side of the head, 24 patients undergoing cardiac catheterization had near-simultaneous determination of CO after indocyanine green dye was injected into the pulmonary artery and left ventricular (LV) cavity. There was close agreement be-

tween pulmonary artery and LV derived cardiac outputs (Pulmonary artery = 0.93 LV + 0.12), The pulmonary artery derived CO was 5.7 4- 2.0 liters/ min and the LV derived CO was 6.1 4- 2.2 liter/ min. Also, there was a close relation between pulmonary artery derived stroke volume (82 4- 33 ml) and LV derived stroke volume (86 4- 36 ml). Thus, CO can be accurately measured after injection of indocyanine green dye into the LV cavity.

As

tions with femoral arterial sampling through a side arm in the arterial sheath, so that measurement of flow could be performed without right-sided cardiac catheterization or the need to enter a second vessel.

(Am J Cardiol 1987;59:142-144)

the indications for cardiac catheterization procedures have evolved from assessment of congenital heart disease and valvular disease to the study of coronary artery disease, the emphasis has shifted from physiologic to anatomic assessment. In many laboratories invasive evaluation of the patient with possible coronary artery disease consists of retrograde arterial catheterization for pressure recording in the LV and aorta, contrast left ventriculography and selective coronary arteriography without assessment of CO. Traditionally, CO measurement requires catheterization of the right side of the heart, either to collect mixed venous blood for oxygen content {Fick principle) or to inject thermal or dye indicators. The Stewart-Hamilton indicator dilution method of determining CO requires that an indicator be thoroughly mixed in blood before sampling at a downstream site. 1 Catheterization of the right side of the heart is no longer routinely performed because it is not considered cost-effective in patients suspected of having only coronary artery disease. This study was performed to determine if CO can be accurately measured from LV indicator injecFrom the Department of Medicine, UCLA School of Medicine, Los Angeles, and the Department of Medicine, Division of Cardiology, Harbor-UCLA Medical Center, Torrance, California. Manuscript received February 28, 1986; revised manuscript received June 17, 1986, accepted June 23, 1986. Address for reprints: William ]. French, MD, Division of Cardiology, Box 4, Harbor-UCLA Medical Center, 1000 West Carson Street, Torrance, California 90509. 142

Methods Patients: These studies were performed in 24 patients {12 men, 12 women} undergoing cardiac catheterization. Mean age was 48 4- 13 years. Cardiac catheterization was performed to evaluate patients with chest pain or to assess the severity of valvular heart disease. All patients underwent right- and left-sided cardiac catheterization, including intracardiac oximetry to rule out intracardiac shunting, CO determination and contrast angiography with injections into the LV cavity as well as into chambers immediately downstream from suspected regurgitant valves. Comparison of cardiac output determination from the pulmonary artery and left ventricle: In all patients measurement of CO was performed after indocyanine green dye had been injected into the pulmonary artery with blood sampling from the sidearm of No. 8Fr femoral arterial sheath. This was followed immediately by injection of green dye into the left ventricle using a No. 7Fr multiple-hole, pigtail catheter to facilitate mixing of indicator with blood in the ventricle. Caution must be taken to avoid an interface air bubble between the green dye injection syringe and the LV catheter. Sampling of blood was also from the femoral artery. The sequence of green dye injections from the pulmonary artery and left ventricle was

January 1, 1987

TABLE I

Clinical,

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Mean -I-SO

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143

Hemodynamlc and Angiographic Data Cardiac Output (liters/min)

Pt

THE AMERICAN JOURNAL OF CARDIOLOGY

Age (yr) & Sex

PA

LV

26M 26M 47M 53F 67F 52M 80M 62F 49M 40F 45M 19F 59F 55F 58F 35F 67F 43M 48M 44F 88M 60F 44M 48M 48 -I- 13

7.9 7.7 5.7 4.8 4.4 6.0 3.2 3.6 4.1 4.3 5.5 5.3 5.7 3.3 7.7 10.9 2.7 7.1 7.9 5.7 4.6 5.8 4.4 8.8 5.7 -I-2.0

8.1 8.3 5:7 4.8 4.7 6.4 4.1 3.8 4.1 4.2 6.1 5.4 5.9 3.6 9.0 12.4 3.8 7.9 8.9 6.8 4.6 5.6 4.6 8.5 6.1 -I-2.2

Heart Rate (beats/min)

Stroke Volume (ml/beat)

PA

LV

PA

62 86 86 61 63 62 102 94 62 58 65 75 81 65 80 60 66 60 93 81 78 60 54 65 71 4-13

63 97 84 65 64 62 104 87 60 60 68 77 81 66 97 61 80 61 90 84 77 63 62 65 73 4-13

128 90 66 79 70 97 31 38 65 73 84 71 71 50 113 181 41 119 84 71 59 96 82 135 82 4-33

LV 128 86 68 73 73 103 39 44 68 70 90 70 73 54 72 203 48 129 99 81 60 89 75 132 86 4-36

EDVI (ml/m 2) 61 136 54 41 106 63 143 98 82 86 95 97 83 73 44 65 87 54 158 66 63 66 83 84 4-30

EF (%)

Angiographic

73 58 71 77 33 57 46 77 79 56 46 54 61 49 72 69 72 71 28 34 68 69 77 59 4-15

Normal 4-I-AR 1VD 1VD I+MR;3VD 2+MR 4+TR;MS;3-i-MR 4-FMR 2VD 1VD 1+MR 4-I-MR 2-FMR 3VD 3VD Normal MS;I+MR;1-I-AR 2VD 1VD 2+MR;1VD 2VD Normal Normal Normal

AR -- aortic regurgitation; EF -- ejection fraction; EDVI = end-diastolic volume index; LV = left ventricle; MR = mitral regurgitation; MS = mitral stenosis; Normal = normal coronary arteries and no valvular regurgitation; PA = pulmonary artery; SD = standard deviation; TR = tricuspid regurgitation; VO = coronary vessel disease.

repeated in duplicate. If the ~ pulmonary artery derived CO measurements were not within 10% of one another, a third set of CO determinations was performed with injection of green dye into the pulmonary artery and left ventricle. If a third set of CO measurements was necessary, only results derived from the last 2 sets of injections were used for statistical analysis. Green dye was injected by hand randomly during the cardiac cycle. Heart rate and femoral artery pressures were recorded before and after each injection of green dye into the pulmonary artery or left ventricle in 10 consecutive patients. Technique of cardiac output determination: Indocyanine green dye (Cardiogreen®), 5 mg in i ml of diluent, was loaded into the LV catheter and manually flushed with 10 ml of heparinized D5W in 2 to 3 seconds as femoral arterial blood was withdrawn through a Gilford densitometer at 40 ml/min from the sidearm of a femoral arterial sheath containing the arterial catheter. CO was computed from the area under the time-density curve using a Lyons computer, previously calibrated with the patient's blank block and 5 mg/ liter concentration of indocyanine green dye. Stroke volume was calculated by dividing CO by the average heart rate obtained during each injection. Data analysis: Data were expressed as mean 4standard deviation. Values for heart rate and stroke volume were rounded to the nearest number. CO data

were analyzed using a paired t test. Differences between CO were analyzed by the Student t test.

Results Clinical: Seventeen of the 24 patients had a normal LV end-diastolic volume index (less than 90 m l / m 2) (Table I). Seven had a reduced ejection fraction (less than 55 % ). Ten patients had regurgitant lesions, which varied from mild to severe. The regurgitant lesions included mitral regurgitation (7 patients), aortic regurgitation (1 patient), mitral and aortic regurgitation (1 patient) and a combination of tricuspid and mitral regurgitation (1 patient).

Comparison of cardiac output determination from the pulmonary artery and left ventricle: There was a close relation between pulmonary artery and LV derived CO in the 24 patients (Pulmonary artery = 0.93 LV + 0.12; r = 0.98, standard error of the estimate ffi 0.49), (Fig. 1). Mean pulmonary artery derived CO was 5.7 4- 2.0 liters/min and the mean LV derived cardiac output was 611 4- 2.2 liters/min. Also, there was close agreement between stroke volume derived from inj ection of green dye into the pulmonary artery (82 4. 33 ml) and from the left ventricle (86 4- 36 ml). The regression equation for stroke volume was close to the line of identity (Pulmonary artery = 0.96 LV + 0.28, r = 0.98, standard error of the estimate = 7.35). In addition, there was no statistically significant difference be-

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CARDIACOUTPUT

tween the average difference of the first pulmonary artery and LV derived CO and between the second :pulmonary artery and LV derived CO (p >0.05). There was no significant difference in heart rate before {72 4- 15 beats/min ] or after (72 4-13) determination of CO or in femoral arterial pressure before {131 426/75 4- 11 mm Hg) or after (129 4- 26/73 4- 14 mm Hg, p <0.05) determination of CO.

Discussion CO is measured infrequently during left-sided cardiac catheterization in patients with coronary artery disease because of the perceived need to perform right-sided cardiac catheterization. This study shows that CO derived from injection of green dye into the left ventricle accurately reflects CO compared with the standard method of injecting green dye into the pulmonary artery. Other studies have reported the use of dilution techniques to estimate CO or ventricular volume after injection of an indicator into the left ventricle. Rapaport 2 used thermodilution techniques to estimate ventricular volume after injection of cold saline solution into the left ventricle. Flamm et al 3 injected green dye into the left ventricle in a small group of patients with atrial septal defects and showed a good correlation

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Acknowledgment:We express our appreciation to Cecelia Hatcher for secretarial assistance in the preparation of this manuscript.

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2 4 6 8 10 12 CARDIAC OUTPUT ( P A - - F A )

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FIGURE 1. Comparison of mean cardiac output measuremenls after injection of green dye Into the pulmonary artery (PA) or left ventricle (LV). FA = femoral artery; SEE = standard error of the estimate.

with Fick derived CO. Wagner, Hughenholtz and their colleagues4-6 were the first to show that CO measured after injection of green dye into the left ventricle approximated the measurement of CO after injection of green dye into the pulmonary artery. Their studies differed from ours in that they used an LV catheter and a second fiberoptic catheter positioned above the aortic valve to measure CO. Our study is in close agreement with the findings of Wagner and Hughenholtz, although we used a single catheter and a commercially available densitometer and green dye computer to measure CO. As in their study, CO derived from LV injections was consistently higher than that derived from right:sided injections, although only by a small amount. A criticism of LV injection of indicator for determination of CO is that there may be incomplete mixing of indicator with blood in the ventricle, which would result in streaming of indicator in the aorta and error in CO measurement. 7 Improper mixing of indicator could lead to either an artifactually small or large curve because the unmixed stream could either be too dilute or too concentrated, resulting in either an overestimation or underestimation of CO, respectively. This study suggests that the sample stream of blood after LV injection of green dye is too dilute, results in a smaller curve area and thus overestimates CO. However, injection of indicator into the right heart or pulmonary artery may underestimate CO because of inability to eliminate recirculation from the first-pass curve. Although small errors in determination of CO may occur after injection of indicator into the right or left side of the heart, both methods probably provide adequate estimation of flow for their respective circulations.

References l. Yang SS, Bentivoglio LG, Maranhao V, Goldberg H. From Catheterization Data to Hemodynamic Parameters. Philadelphia: FA Davis. 1978:62. 2. Rapaport E. Usefulness and limitations of thermal washout techniques in ventricular volume measurement. Am J Cardiol 1966;18:226-234. 3. Flamm MD, Cohn KE, Hancock EW. Measurement of systemic cardiac output at rest and exercise in patients with atrial septal defect. Am l Cardiol 1969;23:258-265, 4. Wagner HR, Gamble WJ, Albers WH, Hugenholtz PG. Fiberaptic-dye dilution method for measurement of cardiac output. Circulation 1968;37:694708. 5. Hugenholtz PG, Gamble WJ, Monroe RG, Polanyi M. The use of fiberoptics in clinical cardiac catheterization. Circulation 1965;31:344-355. 6. Hugenholtz PG, Wagner HR, Sandler H. The in vivo determination of left ventricular volume. Circulation 1968;37:489-508. 7. Holt JP. Indicator-dilution methods: indication, injection, sampling and mixing problems in measurement of ventricular volume. Am f Cardiol 1966;16:208-225.