Preservation of left ventricular function during coronary artery bypass graft surgery

Effects of hypothermic potassium cardioplegia on left ventricular performance and myocardial damage were assessed in 35 patients undergoing coronary artery bypass surgery. Hemodynamic data and enzymatic evidence of left ventricular ischemic damage were examined and compared in the immediate postoperative period. Left ventricular stroke work index showed a significant depression during the first hour with gradual recovery and a significant increase after 24 h. Myocardial specific isoenzyme creatine kinase (CK-MB) showed a very good nonlinear relationship with stroke work index within the whole range, whereas lactate dehydrogenase isoenzyme (LDH-I) had no relationship with the stroke work index. There was a high incidence of transient postoperative arrhythmias and electrical activity took a long time to stabilize. Left ventricular ultrastructure was generally well preserved. The results of this study demonstrate adequate structural and functional preservation of left ventricle by hypothermic potassium cardioplegia.     

Effects of uncomplicated coronary artery bypass graft surgery on global and regional left ventricular function at rest. Study by equilibrium radionuclide angiocardiography

To evaluate the effects of uncomplicated revascularization surgery on resting global and regional left ventricular function we studied 34 patients, enrolled consecutively, by radionuclide angiocardiography. After surgery, we found no significant change in global left ventricular ejection fraction; this was true even in the subgroup of 14 patients who developed paradoxical septal motion. This finding indicates that the development of paradoxical septal motion after uncomplicated cardiac surgery does not compromise global left ventricular function. Both in the subgroup of patients with paradoxical septal motion and in the subgroup without paradoxical septal motion regional ejection fraction calculations showed the same postoperative pattern consisting of increase of the proximal and distal posterolateral regional ejection fraction, increase in the inferoapical regional ejection fraction and unchanged proximal and distal septal regional ejection fraction. In our patients paradoxical septal motion is not due to pericardial effusion, conduction disturbance, septal ischemia or infarction. Our data suggest that the anteromedial translation of the entire heart during systole, due to surgical removal of constraints, may account for both the false improvement of posterolateral and inferoapical regional wall motion and the development of paradoxical septal motion.     

Radionuclide angiographic evaluation of left ventricular performance at rest and during exercise in patients with aortic regurgitation

Radionuclide angiographic evaluation of LV performance at rest and during exercise in patients with AR have shown that an abnormal EF response to exercise may be observed in asymptomatic patients with normal resting LV function. The EF response to exercise has been correlated with a number of clinical and exercise measurements; important among these are the slope of the systolic pressure-to-end-systolic volume, end-systolic volume, cardiac index, pulmonary capillary wedge pressure, and wall stress. The changes in the regurgitant fraction, EF, and LV volume have shown considerable individual variability; they have also allowed a better understanding of the circulatory responses during exercise. Radionuclide angiography provides a reliable and reproducible method of measuring the rest LVEF that is important in the timing and the outcome of valve replacement. The value of the EF response to exercise in patient management is not yet clear; it is possible that other radionuclide-derived measurements at rest or during exercise, such as the systolic pressure-to-end-systolic volume relationship, and the end-systolic volume may provide complementary information to that provided by the EF.     

Regional ventricular function at rest during exercise before and after bypass surgery (author's transl)]

In 9 patients with coronary heart disease isovolumetric contractility indices and ejection phase parameters were measured simultaneously, using an angiographic catheter with a manometer at the tip (Millar). Regional wall motion at rest, after leg raising and during physical exercise (bicycle ergometer) was analyzed applying the hemiaxis method. Five weeks after aortocoronary bypass surgery the same examinations were repeated. Preoperatively left ventricular enddiastolic pressure (LVEDP) increased from 21 to 37 mm Hg following leg raising. The velocity mean of fiber shortening (Vcf) and of regional fiber shortening in the anterior wall decreased significantly.--All patients discontinued physical exercise due to angina pectoris. LVEDP increased from 21 to 39 mm Hg. Large hypokinetic and akinetic areas developed especially in the anterior wall. Velocity of fiber shortening of the anterior wall decreased from 1.43 to 0.76/s. Enddiastolic volume remained unchanged while endsystolic volume increased significantly. In six patients with patent grafts surgery had a beneficial effect. Comparing angiograms at rest no significant changes were found. After leg raising and physical exercise, however, marked improvement in ventricular function occurred, compared to the preoperative performance. All 6 patients were exercised without complaints at a load of 100 watts for 8 minutes. Velocity of fiber shortening in the anterior wall increased significantly from 0.76 to 2.56/s, mean Vcf from 1.11 to 2.12 circ/s, max dP/dt from 2302 to 4280 mm Hg/s and Vpm from 27.8 to 55.7/s. Functional improvement in individual wall segments amounted to 500% in the mean. Ejection fraction increased from 54 to 76%. Enddiastolic volume remained unchanged while endsystolic volume decreased from 67 to 33 ml/1.37 m2 (p less than 0.002). In three patients the bypass occluded or myocardial infarction occurred intraoperatively. Postoperative findings at rest and during exercise were unchanged as compared to preoperative values. Following successful bypass surgery ventricular function at rest did not change. During exercise, however, a marked improvement in overall and in regional ventricular function was found.     

Exercise radionuclide assessment of left ventricular function before and after coronary bypass surgery

The effects of elective saphenous vein coronary artery bypass surgery on left ventricular ejection fraction were assessed by using exercise first-pass radionuclide angiography in 66 consecutive patients. All patients with left main coronary artery or concomitant valvular disease were eliminated from the study. Before surgery, 7 patients had normal postexercise left ventricular function (Group 1), 33 had normal resting left ventricular function with an abnormal response to exercise (Group 2), and 26 had an abnormal resting left ventricular ejection fraction with an abnormal response to exercise (Group 3). Following surgery, patients in all three groups had no change in mean resting left ventricular ejection fraction; however, patients in Groups 2 and 3 had significant improvement in mean postexercise left ventricular ejection fraction (p less than 0.0001 and p less than 0.0054 respectively), whereas patients in Group 1 did not. Previous studies reported improvement in postexercise ejection fraction in patients with reduced resting left ventricular function and with an ischemic response to exercise (Group 3). But this is the first study to confirm improvement in postexercise function in patients with normal resting function and an ischemic response to exercise (Group 2).     

Radionuclide angiographic assessment of left ventricular function during exercise in patients with a severely reduced ejection fraction

To study the effect of exercise on left ventricular ejection fraction in patients with congestive cardiomyopathy and the relation of the response to the origin of the myocardial dysfunction, 30 patients with a severely reduced ejection fraction (30 percent or less) were evaluated with radionuclide angiography. Group I consisted of 16 patients with ischemic cardiomyopathy and a mean (± standard deviation) resting ejection fraction of 22.3 ± 6.1 percent. Group II was composed of 14 patients with primary cardiomyopathy and a mean resting ejection fraction of 19.3 ± 4.7 percent. The mean age, left ventricular end-diastolic pressure, cardiac index and resting left ventricular ejection fraction of Groups I and II were similar; however, the change in the ejection fraction during similar levels of exercise differed significantly. The mean exercise ejection fraction decreased to 16.7 ± 6.8 percent in Group I, but increased to 24.6 ± 6.4 percent in Group II (p < 0.001). Thus, exercise usually results in a directionally opposite change in left ventricular ejection fraction depending on the origin of the congestive cardiomyopathy.     

Radionuclide assessment of left ventricular function during dobutamine infusion in patients with coronary artery disease: comparison with ergometer exercise

The effects of dobutamine on left ventricular function were assessed employing radionuclide ventriculography (RNV) in 7 normal subjects (Group 1) and 21 patients with coronary artery disease (Group 2). After routine bicycle ergometer exercise RNV, dobutamine infusion was started at 5 micrograms/kg/min and the dosage was increased by 5 micrograms/kg/min every 4 minutes to a total of 15 micrograms/kg/min. In Group 1, left ventricular ejection fraction (LVEF) increased by both ergometer exercise and dobutamine infusion. In Group 2, LVEF did not increase during exercise, but increased during dobutamine infusion without evidence of significant myocardial ischemia. Only 2 patients in Group 2 had new regional wall motion abnormality. Left ventricular end-diastolic volume (LVEDV) in Group 2 increased from 191 +/- 19 to 210 +/- 18 ml during ergometer exercise, but decreased from 193 +/- 18 to 153 +/- 19 ml during dobutamine infusion. Short-term low-dose infusion of dobutamine may be used in patients without evidence of significant myocardial ischemia, but probably cannot be substituted for exercise testing in patients with mild to moderate coronary artery disease.     

Radionuclide evaluation of ventricular function at rest and during exercise in double inlet ventricle

We studied ventricular volumes and ejection fraction by radionuclide angiography (equilibrium technique) in 15 patients (aged 3-48 years) with double inlet ventricle not yet submitted to corrective surgery. The end-diastolic volume (measured in nine cases) ranged from 108 to 219 ml/m2 (156 +/- 32), being lower than the normal theoretical value (right plus left ventricle) in six cases. Ejection fraction ranged from 30 to 77% (56.4 +/- 13). The value was significantly higher in the subgroup of 10 patients with a dominant left ventricle as compared to the five cases with dominant right or indeterminate ventricular morphology (63.2 +/- 8.3 versus 42.8 +/- 9, P less than 0.01). In seven of the 15 patients, measurements were obtained both at rest and during dynamic exercise in the semi-upright position. The end-diastolic and end-systolic volumes, stroke volume, ejection fraction underwent a slight non-significant reduction (from 158 +/- 29 to 147 +/- 24 ml/m2, from 58 +/- 16 to 56 +/- 24 ml/m2, from 100 +/- 27 to 90 +/- 24 ml/m2, from 64% +/- 9 to 61% +/- 13). During exercise, ventricular volumes mostly behaved as follows: slight reduction of end-systolic volume, decrease of end-diastolic volume, no increase (no change or decrease) of ejection fraction.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pulmonary function 4 months after coronary artery bypass graft surgery

The objective of this study was to describe the pulmonary function and pain 4 months after coronary artery bypass graft surgery. Twenty-five male patients performed pulmonary function tests before surgery, on the 4th postoperative day and 4 months after surgery. A severe reduction in pulmonary function was present after surgery. Four months postoperatively, the patients still showed a significant decrease (6-13% of preoperative values) in vital capacity (P<0.001), inspiratory capacity (P<0.001), forced expiratory volume in 1 s (P<0.001) peak expiratory flow rate (P<0.001), functional residual capacity (P=0.05) total lung capacity (P<0.001) and single-breath carbon monoxide diffusing capacity (P<0.01). Residual volume and single-breath carbon monoxide diffusing capacity per litre of alveolar volume had returned to the preoperative level. Four months postoperatively, the median values for sternotomy pain while taking a deep breath was 0.2 and while coughing 0.3 on a 10 cm visual analogue pain scale. In conclusion, a significant restrictive pulmonary impairment persisting up to 4 months into the postoperative period was found after CABG. Measured levels of pain were low and could not explain the impairment.     

Acute effects of sublingual nifedipine on segmental and global left ventricular function in coronary artery disease; an angiographic study

In 12 patients with significant coronary artery disease (CAD) segmental and global left ventricular (LV) function was studied by quantitative cineventriculography before and 5 min after sublingual administration of 20 mg nifedipine (N). Significant increase of mean relative hemiaxes shortening of inferior (24 +/- 10%----38 +/- 13%) and apical (31 +/- 10%----42 +/- 14%) wall segments, as well as improvement of ejection fraction (61 +/- 14%----75 +/- 14%), mean circumferential fiber shortening velocity (1.05 +/- 0.46 ccf/s----1.41 +/- 0.47 ccf/s) and end-systolic volume (57 +/- 26 ml----37 +/- 27 ml) of the LV were found after administration of N. The highest increase of segmental contraction (28 +/- 11%----44 +/- 16%; p less than 0.001) was noted in 20 noninfarcted wall segments, perfused by significantly stenosed coronary arteries. No significant improvement could be detected in 6 infarcted segments. A second group consisting of 12 patients with CAD showed a significant reduction of the aortic end-diastolic pressure (89 +/- 9 mm Hg----79 +/- 7 mm Hg; p less than 0.001) but no significant change of isovolumic contractility indices and heart rate was observed after N administration. The study suggests that acute improvement of LV function, found 5 min after sublingual administration of N, is mainly due to improved contraction of ischemic myocardial wall segments. Among different possible reasons for this improvement LV afterload reduction after N administration seems to be the most important one.     

Clinical and angiographic prediction of cardiac death after coronary artery bypass graft surgery.

OBJECTIVES--To study the risk factors for cardiac mortality after coronary artery bypass graft surgery. DESIGN AND SETTING--Follow up study of patients who had undergone coronary artery bypass graft surgery at the University Hospital of Oulu, Finland. PATIENTS AND INTERVENTIONS--339 consecutive patients who underwent cardiac catheterisation three months after bypass surgery. MAIN OUTCOME MEASURES--Incidence of cardiac deaths during the follow up period of five years and predictive value of clinical and angiographic variables for subsequent cardiac mortality. RESULTS--The incidence of cardiac deaths was 5.1%, and 81% of these were sudden deaths. The postoperative ejection fraction was significantly lower in the patients with subsequent cardiac death than in the survivors (p less than 0.001), and their left ventricular end systolic and end diastolic volumes were higher (p less than 0.001 and p less than 0.05 respectively). The incidence of cardiac deaths was 43% in the patients with a postoperative ejection fraction of less than 40%. The myocardial jeopardy index after surgery and the rate of graft patency were not significantly different in the survivors and patients who died. The only clinical factors that were different between the groups were postoperative use of diuretics (p less than 0.001) or digitalis (p = 0.02). After adjustment for other prognostic variables by the proportional hazards method, a low postoperative ejection fraction remained significant as a predictor of the relative risk of cardiac mortality five years after operation (p less than 0.01). CONCLUSIONS--Patients with angiographic evidence of impaired left ventricular function after bypass surgery are still at relatively high risk of dying suddenly, but myocardial ischaemia due to incomplete revascularisation is not strongly associated with an increased risk of cardiac mortality. Conventional clinical methods do not seem to be helpful for identifying patients with an increased risk of cardiac death after bypass surgery.     

Clinical and angiographic prediction of cardiac death after coronary artery bypass graft surgery.

OBJECTIVES--To study the risk factors for cardiac mortality after coronary artery bypass graft surgery. DESIGN AND SETTING--Follow up study of patients who had undergone coronary artery bypass graft surgery at the University Hospital of Oulu, Finland. PATIENTS AND INTERVENTIONS--339 consecutive patients who underwent cardiac catheterisation three months after bypass surgery. MAIN OUTCOME MEASURES--Incidence of cardiac deaths during the follow up period of five years and predictive value of clinical and angiographic variables for subsequent cardiac mortality. RESULTS--The incidence of cardiac deaths was 5.1%, and 81% of these were sudden deaths. The postoperative ejection fraction was significantly lower in the patients with subsequent cardiac death than in the survivors (p less than 0.001), and their left ventricular end systolic and end diastolic volumes were higher (p less than 0.001 and p less than 0.05 respectively). The incidence of cardiac deaths was 43% in the patients with a postoperative ejection fraction of less than 40%. The myocardial jeopardy index after surgery and the rate of graft patency were not significantly different in the survivors and patients who died. The only clinical factors that were different between the groups were postoperative use of diuretics (p less than 0.001) or digitalis (p = 0.02). After adjustment for other prognostic variables by the proportional hazards method, a low postoperative ejection fraction remained significant as a predictor of the relative risk of cardiac mortality five years after operation (p less than 0.01). CONCLUSIONS--Patients with angiographic evidence of impaired left ventricular function after bypass surgery are still at relatively high risk of dying suddenly, but myocardial ischaemia due to incomplete revascularisation is not strongly associated with an increased risk of cardiac mortality. Conventional clinical methods do not seem to be helpful for identifying patients with an increased risk of cardiac death after bypass surgery.     

Accuracy of diagnosis of coronary artery disease by radionuclide management of left ventricular function during rest and exercise

Rest and exercise radionuclide angiocardiographic measurements of left ventricular function were obtained in 496 patients who underwent cardiac catheterization for chest pain. Two hundred forty-eight of these patients also had an exercise treadmill test. An ejection fraction less than 50% was the abnormality of resting left ventricular function that provided the greatest diagnostic information. In patients with normal resting left ventricular function, exercise abnormalities that were optimal for diagnosis of coronary artery disease were an injection fraction at least 6% less than predicted, an increase greater than 20 ml in end-systolic volume and the appearance of an exercise-induced wall motion abnormality. The sensitivity and specificity of the test were lower in patients who were taking propranolol at the time of study and in patients who failed to achieve an adequate exercise end point. In the 387 patients with an optimal study, the test had a sensitivity of 90% and a specificity of 58%. Radionuclide angiocardiography was more sensitive and less specific than the exercise treadmill test. The high degree of sensitivity of the radionuclide test suggests that it is most appropriately applied to patient groups with a high prevalence of disease, including those considered for cardiac catheterization.     

Effects of transluminal coronary angioplasty on left ventricular systolic and diastolic function at rest and during exercise

The left ventricular global and regional systolic function, ventricular volumes, and peak diastolic filling rate (PDFR) were studied in 30 patients with coronary artery disease, before and 2 to 5 days after transluminal coronary angioplasty (PTCA), utilizing equilibrium radionuclide angiography at rest and during exercise. At rest, the global ejection fraction (EF) was unchanged before (60 ± 9%) and after PTCA (62 ± 10%). During exercise, global EF increased from 59 ± 11% pre PTCA to 67 ± 10 post PTCA (p < 0.001). Twenty-two patients had abnormal EF response to exercise pre PTCA, versus seven post PTCA (p < 0.001). Improvements in exercise regional EF paralleled the changes in global EF. End-systolic volume was unchanged at rest but decreased significantly with exercise post PTCA (60 ± 36 ml pre vs 49 ± 32 ml post PTCA, p < 0.01). At rest, the PDFR was unchanged post PTCA (2.4 ± 0.9 end-diastolic volume (EDV)/sec pre vs 2.5 ± 0.8 EDV/sec post). During exercise, PDFR increased from 2.1 ± 0.7 EDV/sec pre PTCA to 2.5 ± 0.7 EDV/sec post PTCA (p < 0.02). In conclusion, in patients with coronary artery disease, successful PTCA improves global and regional systolic function during exercise. Diastolic function is improved during exercise, a fact not previously demonstrated.     

Independence of left ventricular pressure-volume ratio from preload in man early after coronary artery bypass graft surgery

The response of the maximum value of the left ventricular pressure-volume ratio to preload augmentation by blood or plasma expanders was studied in 11 patients during the first 24 hr after coronary artery bypass graft surgery. Increasing the mean left atrial pressure from 10 to 15 and 20 mm Hg resulted in no change in the maximum pressure-volume ratio in the group as a whole. In certain individual patients, however, the maximum pressure-volume ratio changed with volume infusion, and these changes were accompanied by simultaneous changes in afterload. The observed changes in pressure-volume ratio were in the same direction as the changes in afterload (systolic pressure), suggesting a dependence of maximum pressure-volume ratio on afterload. These results show that the maximum pressure-volume ratio is independent of preload in the first 24 hr after coronary artery bypass graft surgery with the pericardium open; thus the maximum pressure-volume ratio is a useful index of postoperative left ventricular function when afterload is unchanged. However, because this ratio (a single-point assessment of the pressure-volume relationship) may not be a good estimate of Emax, we recommend a more complete determination of the locus of the "upper left corners" of the pressure-volume loops for measurement of Emax to provide a more accurate indicator of the myocardial contractile state.     

Impairment of left atrial function predicts post-operative atrial fibrillation after coronary artery bypass graft surgery.

AIMS: Despite the prevalence of atrial fibrillation (AF) occurring after cardiac surgery, its pathophysiology is incompletely understood. Specifically, whether left atrial (LA) structural remodelling occurs, contributing to a decrement in atrial function and AF has not been previously determined. This study sought to determine the relationship between LA function and post-operative AF. METHODS AND RESULTS: Three hundred patients undergoing elective coronary artery bypass graft surgery were monitored with intraoperative transoesophageal echocardiography to determine LA function and dimensions. Post-operative AF was monitored with continuous telemetry until hospital discharge. The relationship between clinical factors versus LA function and dimension was assessed using multi-variate logistic regression. By univariate analysis, patients who subsequently developed post-operative AF had a larger LA area and LA appendage area, and lower LA ejection fraction measured in the pre-bypass period compared to those without subsequent AF. By multivariable analysis, in addition to clinical data including age (odds ratio [OR] 1.11, 95% confidence interval [CI] 1.05-1.16, P<0.0001), body surface area (OR 13.31, 95% CI 1.87-94.5, P=0.0097) and white race, post-bypass atrial systolic function (atrial filling fraction 0.36, OR 2.51, 95% CI 1.03-6.13, P=0.04) and abnormal relaxation of the left ventricle (E duration 270 ms) (OR 2.89, 95% CI 1.34-6.24, P=0.0067) independently increased the risk of post-operative AF. CONCLUSION: These results demonstrate that some of the structural and functional changes in the atria common to chronic AF in the elderly population are also prevalent in surgical patients who develop post-operative AF, suggesting that post-operative and chronic AF may have similar pathophysiology.