Significance
of Cardiac Function in Surgical Management
of
Patients With Valvular Heart Disease HOOSHANG
BOLOOKI,
MD,
FRCS(C),
FACC’ GERARD
KAISER,
MD,
FACC
Miami, Florida
Preoperative cardiac catheterization and hemodynamic studies were expected to clarify two points: first, to confirm the clinical diagnosis and to establish the need for surgical intervention and, second, to indicate the extent of myocardial failure, thereby suggesting the immediate and late prognosis-separating the good hearts from the bad. Because clinical judgment alone could not assess the extent of myocardial reserve in all patients, hemodynamic studies were expected to identify patients who could not be recognized clinically as high operative risks. Unfortunately, in spite of a variety of available invasive and noninvasive study methods, differentiation of high and low risk patients has not been possible in all instances. The cardiac surgeon should therefore evaluate the preoperative hemodynamic studies in an attempt to solve two problems: (1) estimation of the immediate operative (hospital) mortality and the in-. herent complications of the operative procedure, and (2) estimation of the quality of late survival after an apparently successful operation. These problems have been the subject of discussion for many years and are particularly difficult to solve in patients with valvular heart disease. Overall cardiac performance is a function of three interrelated and coordinated systems: The heart (the pump), the peripheral vascular system (the afterload) and the circulating blood volume (homeostatic system and preload). The compensatory effects of each of these systems upon the failure of either of the other is very complex. For example, in a patient who has a high level of left ventricular end-diastolic pressure and a near normal cardiac output, this apparently favorable state of cardiac function may be a result of low peripheral resistance with high end-diastolic From the Division of Thoracic and Cardiovascular Surgery, University of Miami School of Medicine, Miami, Fla. This study was supported in part by grants from the Florida Heart Association and Greater Miami Heart Association, Miami, Fla. and Eli Lilly Research Laboratories, Indianapolis, Ind. * Recipient of Career Development Award, Grant H-5712 from the National Institutes of Health. Address for reprints: Gerard Kaiser, MD, Division of Thoracic and Cardiovascular Surgery, University of Miami School of Medicine, P.O. Box 520875, Biscayne Annex, Miami, Fla. 33152.
February
volume. This condition may not prevail in the period immediately after cardiopulmonary bypass. As a result, immediately after valve replacement, especially if the condition was that of valvular insufficiency (low afterload) and was corrected by a competent valve (high afterload), the abnormal preoperative physioiogy may not persist. Therefore, heart failure may ensue, not because of intraoperative technical circumstances but because of the unrecognized poor myocardial reserve preoperatively. Value of Monitoring Cardiac Function Indexes in the Early Postoperative Period Although no single index of cardiac function would in all cases predict the outcome of an operative procedure, it is now believed that a correlation between the clinical status of the patient and performance of the heart as a muscle and as a pump is necessary to justify surgical intervention and to prognosticate early and late results. A few years ago, we were intrigued by the finding that indexes of myocardial contractility (force-velocity relation) derived from the isometric indexes of left ventricular contraction might be independent of left ventricular preload and afterload. Excellent clinical studies by Hugenholtz et a1.l on follow-up of children evaluated by this method indicated that the technique had a prognostic value. These findings were later confirmed by others, but soon the dependency of these indexes upon changes in preload was criticized and the formula used to evaluate force-velocity indexes was considered inaccurate.2 As a result, we used this method of study for the immediate postoperative care of patients.3 On serial and on line follow-up of velocity indexes during the postoperative period, we frequently found changes in values with no clinical indication that the patient’s cardiac status had changed. In fact, the clinical setting, together with blood pressure, urinary output and central venous pressure determinations, always dictated therapy. If the clinical findings were normal, a decrease in contractility indexes did not force us to institute any interventions. In a later study we compared the value of indexes of cardiac muscle performance (force-velocity index-
1976
The American
Journal of CARDIOLOGY
Volume
37
319
EDITORIALS
es) with those of cardiac pump function (cardiac index, end-diastolic pressure and volume). The latter indexes always correlated better with the clinical setting in the immediate postoperative period. Thus, we concluded that assessment of left ventricular enddiastolic pressure (or pulmonary wedge pressure or left atria1 mean pressure) with changes in cardiac, output would be of more value than indexes of cardiac muscle performance in the immediate postoperative care of patients. It followed that some patients with a high cardiac index died with hypotension and without an excessive elevation of preload (left ventricular diastolic pressure) in spite of massive inotropit intervention, as found some 10 years ago by Rastelli and Kirklin.5 But in the majority of patients, clinical judgment (the patient’s condition, blood pressure, urinary output and central venous pressure) led to the correct diagnosis of postoperative heart pump failure and the need for proper treatment. Difficulties remained for patients whose clinical status and hemodynamic findings were at variance. In these patients we resorted to measurement of cardiac output by the Swan-Ganz catheter and thermodilution technique. However, in a small percentage of patients cardiac output studies alone were inadequate, and other means of monitoring cardiac function were needed. Specific to this situation were patients who had a remarkable initial recovery from cardiopulmonary bypass with acceptable hemodynamic status but a few hours later manifested the socalled low output syndrome. In this issue of the Journal, Appelbaum et al.” describe their data on early risks of open mitral valve surgery, applying the concept of assessment of cardiac pump function. Their surgical results are excellent considering the number of their patients who were in New York Heart Association functional class IV before operation. They emphasize the need for hemodynamic studies in patients who immediately after operation have depressed cardiac performance and re-
.
I
EARLYOtATHLAU DEATH SURVIVORS
I
February
1976
The American
Prognostic
I
tAALV DEATH1AltMATH SURVIVORS
FIGURE 1. The relation between early (hospital) and late (within 2 years after operation) death and survival and myocardial contractility (Vmax)” and ejection fraction. The data were obtained from 87 patients with aortic or mitral valve disease, or both, undergoing valve replacement. The solid horizontal bars indicate the mean value for each category of patients. The probability (p) value compares the data for survivors (more than 2 years) with those for patients who died early or late postoperatively.
320
quire inotropic agents. They conclude that in those patients whose cardiac index is less than 1 liter/min per m2 preoperatively, the operative mortality rate is remarkably high in spite of apparent correction of the valvular lesion. Similiarly, patients with a depressed cardiac index postoperatively have the highest early mortality rate. An evaluation of the early risks of open mitral valve surgery in these patients based on three important variables, functional class, cardiac index and pulmonary arterial oxygen pressure, disclosed a direct relation between functional class and cardiac index and early death. There was no correlation between pulmonary arterial hypertension and left ventricular end-diastolic pressure and early surgical outcome. On the basis of their findings, Appelbaum et al. relate the early risk in these patients to preservation of sufficient cardiac index and the need to operate while the patient’s functional class is class III or lower. Litwak et a1.7 and Najafi et a1.s reached similar conclusions. It is obvious, however, that patients with a cardiac index of less than 1.4 preoperatively most likely are in functional class III or IV. Therefore, it seems doubtful that cardiac index alone would prognosticate the outcome of the operation better than the subjective functional classification. Because of this need to evaluate combined data it seems justified to utilize the best available method of postoperative hemodynamic monitoring in the care of the patients with a low preoperative cardiac index and those in functional class III or IV. Some surgical groups, including ours, now use elective intraaortic balloon pump assist to improve operative survival in patients selected on the basis of preoperative cardiac function,
Journal of CARDIOLOGY
Value of Hemodynamic
Indexes
The long-term results of valvular heart surgery based on preoperative or immediate postoperative cardiac function studies have not been extensively evaluated. One such study9 recently indicated that the best prognosticators of eventual outcome are the preoperative clinical functional class and the cardiac index. Other hemodynamic data showed less prognostic significance. Surprisingly, an index such as left ventricular end-diastolic pressure was a poor indicator of the risk of late development of cardiac failure and death in patients undergoing mitral valve replacement. Bonchek et al. lo also showed that the preoperative functional class was the best indicator of long-term results. Najafi et a1.s and Litwak et a1.7 indicated that conditions such as reoperation, dysrhythmia and atria1 fibrillation, enlarged heart and preoperative congestive heart failure adversely affect the long-term results of valvular heart disease after surgery. In an attempt to clarify a similar point, some 23 indexes of cardiac function from preoperative cardiac catheterization studies in a group of 87 patients were evaluated. These were then related to the operative mortality and late death rates. After exclusion of rare
Volume
37
EDITORIALS
intraoperative technical problems, patients who died within the postoperative period (30 days) and those who died in the course of 3 years of follow-up study were evaluated in a consecutive fashion. This group was composed of patients with mitral and aortic valve disease alone or in combination. We found that the prognostic value of various indexes of cardiac function was such that patients with more severe cardiac dysfunction had higher operative and late mortality rates, but the point of differentiation for various hemodynamic data was not clearly delineated. Of various measures of cardiac function, cardiac index and contractility indexes (Vmax)ll provided better differentiation than other values for operative and late (longer than 3 years) survival (Fig. 1). All patients with a preoperative Vmax value of more than 2.2 circumferenceslsec survived longer than 3 years after the operation whereas patients with a Vmax of less than 2.2 had an early mortality rate of approximately 7 percent and a late mortality rate of 20 percent. In a similar study of preoperative ejection fraction (Fig. 1) the probability of early and late death for patients with an ejection fraction value greater than 40 percent was 5 and 10 percent, respectively, as compared with 30 and 25 percent in patients with a lower ejection fraction. Surprisingly, the cutoff value for cardiac index was 2.4 liters/min per m2, a value
similar to that of the patients et a1.6
studied by Appelbaum
Conclusions We now believe that extensive monitoring with left ventricular or left atria1 pressure recordings, SwanGanz catheter insertion and cardiac output measurement is necessary only in patients who have congestive heart failure preoperatively, a cardiac index of less than 2 liters/min per m2, an ejection fraction of less than 40 percent or an apparently unsatisfactory cardiac function status immediately after cardiopulmonary bypass, All other patients can be cared for with hemodynamic monitoring limited to on-line arterial, central venous or left atria1 pressure recordings, alone or in combination, together with evaluation of pulmonary and renal function. We believe the preoperative hemodynamic measurements, especially the contractility indexes, are the most important prognostic indicators of late survival of surgery for valvular heart disease. We emphasize, as Appelbaum et a1.6 have done, the need for careful evaluation of the pre- and postoperative hemodynamic data by the cardiac surgical team. In this manner the patient who is at high risk may be differentiated and all the available monitoring techniques and circulatory assist methods used on a selective basis.
References 1. Hugenholtz PO, Elllson RC, Mlrsky I, et al: Myocardial force2.
3.
4.
5.
6.
velocity relationship in clinical heart disease. Circulation 41: 191-202,197o Noble MM: Problems concerning the application of concepts of muscle mechanics to the determination of the contractile state of the heart. Circulation 45:252-255, 1972 Bolooki H, Ghahramani A, Sommer L, et al: Continuous monitoring of myocardial contractility (abstr). Am J Cardiol 9:254, 1972 Bolooki H, Vargas A, Kaiser GA, et al: Cardiac function in cardisc surgery patients. In Special Issue of the Journal of Cardiovascular Surgery of the XI World Congress of the International Cardiovascular Society, Barcelona, Spain, September 27-29, 1973 (Arias AR, ed), Torino, Italy, Edizioni Minerva Medica, 1975, p 661-666 Rastelli GC, Kirklln JW: Hemodynamic state early after prosthetic replacement of mitral valve. Circulation 34:448-461, 1966 Appelbaum A, Kouchoukos NT, Blackstone EH, et al: Early
7.
8.
9.
10.
11.
February 1976
risks of open mitral valve surgery. Am J Cardiol 37:201-209. 1976 Lltwak RC, Sllvay J, Gadboys HL, et al: Factors associated with operative risk in mitral replacement. Am J Cardiol 23: 335-348, 1969 Najafl H, Dye WS, Javld H, et al: Mitral valve replacement. Review of seven years’ experience. Am J Cardiol 24:386-392, 1969 Hlrshfeld JW Jr, Epstein SE, Roberts AJ, et al: Indices predicting long-term survival after valve replacement in patients with aortic regurgitation and patients with aortic stenosis. Circulation 50:1190-1199‘1974 Bonchek Ll, Anderson RP, Starr A: Mitral valve replacement with cloth-covered composite-seat prosthesis. J Thorac Cardiovast Surg 67:93-109. I974 Bolookl H, Rublnson RM, Mlchle DD, et al: Assessment of myocardial contractility after coronary bypass grafts. J Thorac Cardiovasc Surg 62:543-553, 1971
The American Journal of CARDIOLOGY
Volume 37
321
of Cardiac Function in Surgical Management
of
Patients With Valvular Heart Disease HOOSHANG
BOLOOKI,
MD,
FRCS(C),
FACC’ GERARD
KAISER,
MD,
FACC
Miami, Florida
Preoperative cardiac catheterization and hemodynamic studies were expected to clarify two points: first, to confirm the clinical diagnosis and to establish the need for surgical intervention and, second, to indicate the extent of myocardial failure, thereby suggesting the immediate and late prognosis-separating the good hearts from the bad. Because clinical judgment alone could not assess the extent of myocardial reserve in all patients, hemodynamic studies were expected to identify patients who could not be recognized clinically as high operative risks. Unfortunately, in spite of a variety of available invasive and noninvasive study methods, differentiation of high and low risk patients has not been possible in all instances. The cardiac surgeon should therefore evaluate the preoperative hemodynamic studies in an attempt to solve two problems: (1) estimation of the immediate operative (hospital) mortality and the in-. herent complications of the operative procedure, and (2) estimation of the quality of late survival after an apparently successful operation. These problems have been the subject of discussion for many years and are particularly difficult to solve in patients with valvular heart disease. Overall cardiac performance is a function of three interrelated and coordinated systems: The heart (the pump), the peripheral vascular system (the afterload) and the circulating blood volume (homeostatic system and preload). The compensatory effects of each of these systems upon the failure of either of the other is very complex. For example, in a patient who has a high level of left ventricular end-diastolic pressure and a near normal cardiac output, this apparently favorable state of cardiac function may be a result of low peripheral resistance with high end-diastolic From the Division of Thoracic and Cardiovascular Surgery, University of Miami School of Medicine, Miami, Fla. This study was supported in part by grants from the Florida Heart Association and Greater Miami Heart Association, Miami, Fla. and Eli Lilly Research Laboratories, Indianapolis, Ind. * Recipient of Career Development Award, Grant H-5712 from the National Institutes of Health. Address for reprints: Gerard Kaiser, MD, Division of Thoracic and Cardiovascular Surgery, University of Miami School of Medicine, P.O. Box 520875, Biscayne Annex, Miami, Fla. 33152.
February
volume. This condition may not prevail in the period immediately after cardiopulmonary bypass. As a result, immediately after valve replacement, especially if the condition was that of valvular insufficiency (low afterload) and was corrected by a competent valve (high afterload), the abnormal preoperative physioiogy may not persist. Therefore, heart failure may ensue, not because of intraoperative technical circumstances but because of the unrecognized poor myocardial reserve preoperatively. Value of Monitoring Cardiac Function Indexes in the Early Postoperative Period Although no single index of cardiac function would in all cases predict the outcome of an operative procedure, it is now believed that a correlation between the clinical status of the patient and performance of the heart as a muscle and as a pump is necessary to justify surgical intervention and to prognosticate early and late results. A few years ago, we were intrigued by the finding that indexes of myocardial contractility (force-velocity relation) derived from the isometric indexes of left ventricular contraction might be independent of left ventricular preload and afterload. Excellent clinical studies by Hugenholtz et a1.l on follow-up of children evaluated by this method indicated that the technique had a prognostic value. These findings were later confirmed by others, but soon the dependency of these indexes upon changes in preload was criticized and the formula used to evaluate force-velocity indexes was considered inaccurate.2 As a result, we used this method of study for the immediate postoperative care of patients.3 On serial and on line follow-up of velocity indexes during the postoperative period, we frequently found changes in values with no clinical indication that the patient’s cardiac status had changed. In fact, the clinical setting, together with blood pressure, urinary output and central venous pressure determinations, always dictated therapy. If the clinical findings were normal, a decrease in contractility indexes did not force us to institute any interventions. In a later study we compared the value of indexes of cardiac muscle performance (force-velocity index-
1976
The American
Journal of CARDIOLOGY
Volume
37
319
EDITORIALS
es) with those of cardiac pump function (cardiac index, end-diastolic pressure and volume). The latter indexes always correlated better with the clinical setting in the immediate postoperative period. Thus, we concluded that assessment of left ventricular enddiastolic pressure (or pulmonary wedge pressure or left atria1 mean pressure) with changes in cardiac, output would be of more value than indexes of cardiac muscle performance in the immediate postoperative care of patients. It followed that some patients with a high cardiac index died with hypotension and without an excessive elevation of preload (left ventricular diastolic pressure) in spite of massive inotropit intervention, as found some 10 years ago by Rastelli and Kirklin.5 But in the majority of patients, clinical judgment (the patient’s condition, blood pressure, urinary output and central venous pressure) led to the correct diagnosis of postoperative heart pump failure and the need for proper treatment. Difficulties remained for patients whose clinical status and hemodynamic findings were at variance. In these patients we resorted to measurement of cardiac output by the Swan-Ganz catheter and thermodilution technique. However, in a small percentage of patients cardiac output studies alone were inadequate, and other means of monitoring cardiac function were needed. Specific to this situation were patients who had a remarkable initial recovery from cardiopulmonary bypass with acceptable hemodynamic status but a few hours later manifested the socalled low output syndrome. In this issue of the Journal, Appelbaum et al.” describe their data on early risks of open mitral valve surgery, applying the concept of assessment of cardiac pump function. Their surgical results are excellent considering the number of their patients who were in New York Heart Association functional class IV before operation. They emphasize the need for hemodynamic studies in patients who immediately after operation have depressed cardiac performance and re-
.
I
EARLYOtATHLAU DEATH SURVIVORS
I
February
1976
The American
Prognostic
I
tAALV DEATH1AltMATH SURVIVORS
FIGURE 1. The relation between early (hospital) and late (within 2 years after operation) death and survival and myocardial contractility (Vmax)” and ejection fraction. The data were obtained from 87 patients with aortic or mitral valve disease, or both, undergoing valve replacement. The solid horizontal bars indicate the mean value for each category of patients. The probability (p) value compares the data for survivors (more than 2 years) with those for patients who died early or late postoperatively.
320
quire inotropic agents. They conclude that in those patients whose cardiac index is less than 1 liter/min per m2 preoperatively, the operative mortality rate is remarkably high in spite of apparent correction of the valvular lesion. Similiarly, patients with a depressed cardiac index postoperatively have the highest early mortality rate. An evaluation of the early risks of open mitral valve surgery in these patients based on three important variables, functional class, cardiac index and pulmonary arterial oxygen pressure, disclosed a direct relation between functional class and cardiac index and early death. There was no correlation between pulmonary arterial hypertension and left ventricular end-diastolic pressure and early surgical outcome. On the basis of their findings, Appelbaum et al. relate the early risk in these patients to preservation of sufficient cardiac index and the need to operate while the patient’s functional class is class III or lower. Litwak et a1.7 and Najafi et a1.s reached similar conclusions. It is obvious, however, that patients with a cardiac index of less than 1.4 preoperatively most likely are in functional class III or IV. Therefore, it seems doubtful that cardiac index alone would prognosticate the outcome of the operation better than the subjective functional classification. Because of this need to evaluate combined data it seems justified to utilize the best available method of postoperative hemodynamic monitoring in the care of the patients with a low preoperative cardiac index and those in functional class III or IV. Some surgical groups, including ours, now use elective intraaortic balloon pump assist to improve operative survival in patients selected on the basis of preoperative cardiac function,
Journal of CARDIOLOGY
Value of Hemodynamic
Indexes
The long-term results of valvular heart surgery based on preoperative or immediate postoperative cardiac function studies have not been extensively evaluated. One such study9 recently indicated that the best prognosticators of eventual outcome are the preoperative clinical functional class and the cardiac index. Other hemodynamic data showed less prognostic significance. Surprisingly, an index such as left ventricular end-diastolic pressure was a poor indicator of the risk of late development of cardiac failure and death in patients undergoing mitral valve replacement. Bonchek et al. lo also showed that the preoperative functional class was the best indicator of long-term results. Najafi et a1.s and Litwak et a1.7 indicated that conditions such as reoperation, dysrhythmia and atria1 fibrillation, enlarged heart and preoperative congestive heart failure adversely affect the long-term results of valvular heart disease after surgery. In an attempt to clarify a similar point, some 23 indexes of cardiac function from preoperative cardiac catheterization studies in a group of 87 patients were evaluated. These were then related to the operative mortality and late death rates. After exclusion of rare
Volume
37
EDITORIALS
intraoperative technical problems, patients who died within the postoperative period (30 days) and those who died in the course of 3 years of follow-up study were evaluated in a consecutive fashion. This group was composed of patients with mitral and aortic valve disease alone or in combination. We found that the prognostic value of various indexes of cardiac function was such that patients with more severe cardiac dysfunction had higher operative and late mortality rates, but the point of differentiation for various hemodynamic data was not clearly delineated. Of various measures of cardiac function, cardiac index and contractility indexes (Vmax)ll provided better differentiation than other values for operative and late (longer than 3 years) survival (Fig. 1). All patients with a preoperative Vmax value of more than 2.2 circumferenceslsec survived longer than 3 years after the operation whereas patients with a Vmax of less than 2.2 had an early mortality rate of approximately 7 percent and a late mortality rate of 20 percent. In a similar study of preoperative ejection fraction (Fig. 1) the probability of early and late death for patients with an ejection fraction value greater than 40 percent was 5 and 10 percent, respectively, as compared with 30 and 25 percent in patients with a lower ejection fraction. Surprisingly, the cutoff value for cardiac index was 2.4 liters/min per m2, a value
similar to that of the patients et a1.6
studied by Appelbaum
Conclusions We now believe that extensive monitoring with left ventricular or left atria1 pressure recordings, SwanGanz catheter insertion and cardiac output measurement is necessary only in patients who have congestive heart failure preoperatively, a cardiac index of less than 2 liters/min per m2, an ejection fraction of less than 40 percent or an apparently unsatisfactory cardiac function status immediately after cardiopulmonary bypass, All other patients can be cared for with hemodynamic monitoring limited to on-line arterial, central venous or left atria1 pressure recordings, alone or in combination, together with evaluation of pulmonary and renal function. We believe the preoperative hemodynamic measurements, especially the contractility indexes, are the most important prognostic indicators of late survival of surgery for valvular heart disease. We emphasize, as Appelbaum et a1.6 have done, the need for careful evaluation of the pre- and postoperative hemodynamic data by the cardiac surgical team. In this manner the patient who is at high risk may be differentiated and all the available monitoring techniques and circulatory assist methods used on a selective basis.
References 1. Hugenholtz PO, Elllson RC, Mlrsky I, et al: Myocardial force2.
3.
4.
5.
6.
velocity relationship in clinical heart disease. Circulation 41: 191-202,197o Noble MM: Problems concerning the application of concepts of muscle mechanics to the determination of the contractile state of the heart. Circulation 45:252-255, 1972 Bolooki H, Ghahramani A, Sommer L, et al: Continuous monitoring of myocardial contractility (abstr). Am J Cardiol 9:254, 1972 Bolooki H, Vargas A, Kaiser GA, et al: Cardiac function in cardisc surgery patients. In Special Issue of the Journal of Cardiovascular Surgery of the XI World Congress of the International Cardiovascular Society, Barcelona, Spain, September 27-29, 1973 (Arias AR, ed), Torino, Italy, Edizioni Minerva Medica, 1975, p 661-666 Rastelli GC, Kirklln JW: Hemodynamic state early after prosthetic replacement of mitral valve. Circulation 34:448-461, 1966 Appelbaum A, Kouchoukos NT, Blackstone EH, et al: Early
7.
8.
9.
10.
11.
February 1976
risks of open mitral valve surgery. Am J Cardiol 37:201-209. 1976 Lltwak RC, Sllvay J, Gadboys HL, et al: Factors associated with operative risk in mitral replacement. Am J Cardiol 23: 335-348, 1969 Najafl H, Dye WS, Javld H, et al: Mitral valve replacement. Review of seven years’ experience. Am J Cardiol 24:386-392, 1969 Hlrshfeld JW Jr, Epstein SE, Roberts AJ, et al: Indices predicting long-term survival after valve replacement in patients with aortic regurgitation and patients with aortic stenosis. Circulation 50:1190-1199‘1974 Bonchek Ll, Anderson RP, Starr A: Mitral valve replacement with cloth-covered composite-seat prosthesis. J Thorac Cardiovast Surg 67:93-109. I974 Bolookl H, Rublnson RM, Mlchle DD, et al: Assessment of myocardial contractility after coronary bypass grafts. J Thorac Cardiovasc Surg 62:543-553, 1971
The American Journal of CARDIOLOGY
Volume 37
321
