Measurement of end-systolic pressure-volume relations by intra-aortic balloon occlusion

A new situ technique has been developed for measuring peak end-systolic elastance, Emax, that does not alter intrinsic or reflex-stimulated cardiac contractility. Afterload is varied by the inflation of an intra-aortic balloon catheter positioned in the ascending aorta. Balloon inflation is timed to interrupt ventricular ejection transiently at different times during the ejection phase, therefore, producing contraction at different ventricular volumes. Simultaneous measurement of left ventricular pressure and aortic flow during the occlusion sequence allows pressure versus ejected volume loops to be generated, from which the end-systolic pressure-volume relation is determined. End-systolic pressure-volume relation (ESPVR) was measured in six anesthetized Dorsett sheep with normal and enhanced contractile states. ESPVR was analyzed using both linear and nonlinear techniques. Although nonlinear components were seen in ESPVR, for the pressure-volume data range produced by the transient occlusions, linear approximations of ESPVR fit the end-systolic data points well. In the normal state, Emax, the slope of the linear ESPVR, was 1.01-5.08 mm Hg/ml in animals with body weights of 23-32 kg. After epinephrine infusion, Emax increased from 3.07 +/- 1.49 to 5.79 +/- 1.97 mm Hg/ml, which is consistent with previous investigations. Linear and nonlinear volume intercepts had a small increase with positive inotropic stimulation. Furthermore, serial measurements of Emax tracked cardiac function in depressed hearts with rapidly changing contractility.

Surgery for left ventricular aneurysm. Early survival with and without endocardial resection

In the past 3 years, 86 patients had left ventricular aneurysms resected or plicated. Sixty-eight had recurrent sustained ventricular tachycardia as the indication for surgery and had preoperative and intraoperative electrophysiologic mapping. There were 14 hospital deaths (16%). Eight preoperative potential risk factors for early hospital mortality were analyzed by multivariate analysis. Only acute myocardial infarction within 30 days before surgery correlated with hospital death at the p less than 0.05 level. History of previous heart surgery and advanced New York Heart Association functional class were important risk factors at the p less than 0.1 level. Hospital mortality was 17.6% for patients who had intraoperative mapping and endocardial resection and 11.1% for the others. Patients who had aneurysm repair for ventricular tachycardia had a significantly higher incidence of low cardiac output early after surgery (p less than 0.025).

Coronary artery bypass grafting in the presence of valvular disease

Compared with isolated coronary artery bypass grafting (CABG), the combination of valve replacement or repair with coronary revascularization generally increases operative risk. However, complete revascularization is superior to no revascularization in patients with valvular and coronary artery disease (CAD). Patients who undergo aortic valve replacement and CABG have two unrelated disease processes; these patients only infrequently have ischemic cardiomyopathy, and the operative mortality is slightly increased to 4-7% for the combined procedure versus isolated aortic valve replacement. Patients who are operated on for mitral valve disease and CAD fall into two groups: 1) where CAD and mitral valve disease are not etiologically related, and 2) where mitral valve dysfunction is the result of ischemic changes. In the latter group, operative mortality significantly exceeds that for isolated mitral valve surgery, and surgical priority increases that difference (operative mortality 7-20%). Thus, the operative risk for a mitral valve procedure plus CABG exceeds that for isolated coronary revascularization or isolated valve replacement. In the combined procedure, risk increases if valve dysfunction is caused by CAD, if severe left ventricular function is present, if the patient has been assigned to Class IV, or if emergency operation is required.

Loss of platelet fibrinogen receptors during clinical cardiopulmonary bypass

In 10 patients, cardiopulmonary bypass decreased the number of fibrinogen binding sites from 31,730 +/- 12,802 per platelet to 18,590 +/- 9,644 per platelet. Bypass also decreased the amount of the platelet membrane glycoprotein IIIa, which is part of the fibrinogen receptor complex, from 17.1 +/- 3.6 ng/10(9) platelets to 12.9 +/- 4.7. The fibrinogen binding constant did not change. Platelet sensitivity to adenosine diphosphate did not change; however, template bleeding times increased from 5.2 +/- 1.5 minutes before bypass to 8.5 +/- 2.3 minutes after bypass. Analysis of detergent washings from the perfusion circuit after bypass in five patients indicated that platelet material remains attached to the surface as membrane fragments and degranulated platelets. These data further elucidate the mechanism of platelet loss and dysfunction during cardiopulmonary bypass and highlight the importance of platelet membrane fibrinogen receptors and surface adsorbed fibrinogen in this process.

Formation of C1s-C1-inhibitor, kallikrein-C1-inhibitor, and plasmin-alpha 2-plasmin-inhibitor complexes during cardiopulmonary bypass

Stimulation of platelets and neutrophils occurs during clinical cardiopulmonary bypass. We investigated whether the classical complement, contact, or fibrinolytic pathways are activated as potential sources of neutrophil agonists. Using enzyme-linked immunosorbent "sandwich" assays specific for C1s-C1-and kallikrein-C1-inhibitor complexes respectively, we found that there was a modest increase in plasma levels of each complex after clinical cardiopulmonary bypass was completed. The increased concentration of enzyme-inhibitor complexes reverted to baseline within 24 hours. Since these complexes are cleared in vivo, we measured their formation by assaying their plasma levels during in vitro simulated extracorporeal circulation. Over a period of two hours, C1s-C1-inhibitor complexes rose from a baseline of 2 +/- 1 nmol/L to 21 +/- 2 nmol/L, and kallikrein-C1-inhibitor complexes rose from 2 +/- 1 nmol/L to 25 +/- 5 nmol/L. However, there was no evidence of either in vivo or in vitro plasmin-alpha 2-plasmin-inhibitor complex formation. These results indicate that the pathways of classical complement and contact activation, but probably not fibrinolysis, may be associated with neutrophil activation seen during clinical cardiopulmonary bypass.

Flow dynamics of peripheral venous catheters during extracorporeal membrane oxygenation with a centrifugal pump

Extracorporeal membrane oxygenation uses peripherally placed cannulas and a streamlined circuit without a venous reservoir. This study tests the flow dynamics of venous catheters connected without a reservoir directly to a centrifugal pump. During in vitro testing, a 30 cm segment of collapsible tubing interposed between the reservoir and pump simulates the vein. In five sheep, flow was measured between catheters placed in the right atrium and inferior vena cava from peripheral sites. Catheter tip design (four types) does not affect flow within a simulated vein in vitro. Maximum pump flow is independent of filling pressures (6 to 21 mm Hg) in vitro and in vivo when the catheter tip is in a tank reservoir or the right atrium. However, when the catheter tip is within a collapsible segment or in the inferior vena cava, maximal flow is significantly influenced by filling pressure (6 to 18 mm Hg) and by the ratio of catheter outer diameter to venous diameter. At all filling pressures, maximal flow in vivo is significantly reduced when this ratio is greater than 0.5. During extracorporeal membrane oxygenation, central venous pressure and catheter/vein ratio, not catheter size alone, control flow through peripheral venous catheters.

Open-heart surgery in octogenarians

One hundred consecutive patients 80 years of age or older consented to and subsequently underwent open-heart operations at our institution between July 1976 and May 1987. Fifty of the patients had aortic valvular disease (28 with coexisting coronary artery disease), and 41 had isolated coronary artery disease. Eight patients had mitral valvular disease, and one had a dissecting aortic aneurysm. Ninety had Class IV disease that was functional, ischemic, or both. The most compelling indications for operation in 85 patients were unstable or postinfarction angina, syncope, acute pulmonary edema, or cardiogenic shock. Twenty-nine patients died soon after operation (within 90 days). New York Heart Association Class IV disease, previous myocardial infarction, cachexia, and emergency operation were preoperative variables associated with early death. Forty-three patients had no complications except for atrial arrhythmias and were discharged from the hospital a mean (+/- SD) of 11.5 +/- 3.7 days after operation. Low cardiac output, acute myocardial infarction, reoperation for bleeding, renal insufficiency, pneumonia, and prolonged endotracheal intubation were the most common serious postoperative complications. Twenty-eight patients who survived postoperative complications were discharged 24.9 +/- 19.6 days after operation. Seventeen patients died 2 to 104 months after discharge from the hospital. Actuarial calculation predicts the survival of 59 percent of patients at three years and 54 percent at five years. Of the 54 patients still alive at this writing, 53 have disease within New York Heart Association and Canadian Cardiovascular Society Classes I or II. For selected octogenarians with unmanageable cardiac symptoms, operation may be an effective therapeutic option.

Changes in left ventricular systolic wall stress during biventricular circulatory assistance

Extracorporeal membrane oxygenation (ECMO) reduces the systolic stress integral (SSI) in the normal left ventricle. We tested the hypothesis that the SSI does not decrease in poorly contracting, dilated, ejecting hearts during ECMO. In 14 sheep, four pairs of ultrasonic crystals measured changes in left ventricular (LV) wall thickness and three LV diameters. Volume calculations were validated by balloon distention of the ventricles after death (slope = 0.85; r = 0.85). SSI was measured during ECMO flows of 20 to 100 ml/kg/min in both normal and dilated, poorly contracting hearts produced by 30 minutes of warm ischemia. After warm ischemia, end-systolic elastance, an index of contractility, decreased from 8.3 +/- 0.6 mm Hg/ml to 2.9 +/- 0.4 mm Hg/ml (p = 0.001) and peak systolic pressure decreased from 47.4 +/- 0.7 mm Hg to 37.5 +/- 0.08 mm Hg (p = 0.01). In normal hearts, as ECMO flow increased, SSI decreased from 10.5 +/- 2.2 mm Hg.sec to 7.7 +/- 0.8 mm Hg.sec at 60 ml/kg/min (p = 0.001). However, in postischemic hearts, SSI progressively increased from 6.6 +/- 0.3 mm Hg.sec before ECMO to 12.4 +/- 1.8 mm Hg.sec at ECMO = 100 ml/kg/min. These studies indicate that the initial effect of ECMO on the poorly contracting, dilated heart increases LV wall stress and that the increase in stress is proportional to ECMO flow. The increase in stress is primarily due to an increase in afterload, which more than offsets decreases in systolic and diastolic volumes.

Clinical comparison of St. Jude and porcine mitral valve prostheses

One hundred and six consecutive patients who had mitral valve replacement with either a St. Jude or porcine heterograft prosthesis were prospectively studied. The 2 groups are similar with respect to 67 clinical and operative factors and allow comparison of valve performance as an independent variable. Total follow-up is 3,312 patient-months (mean 36 months, range 2-57 months, 94% complete). There are no statistical differences in symptomatic improvement or mortality by life table analysis. Valve-related complications expressed as percent per patient-year are: reoperation: 1.8 St. Jude and 3.8 porcine; endocarditis: 1.2 and 1.9; regurgitant murmur: 2.3 and 1.9; hemolysis: 1.8 and 0.0; late thromboembolism: 1.8 and 1.0; hemorrhage: 2.9 and 2.9; and valve failure: 0.0 and 1.0. There were no significant differences found. Actuarial survival at 3 years was 78% in St. Jude and 81% in porcine patients. Forty-six percent of patients with St. Jude valves and 55% of patients with porcine valves were alive and free of all complications at latest follow-up. The clinical performance of St. Jude and porcine mitral valves are similar over this period of intermediate follow-up.

Simultaneous implantation of St. Jude Medical aortic and mitral prostheses

Since January 1980, 92 consecutive patients received St. Jude Medical aortic and mitral prostheses simultaneously. Mean age was 57.6 years (standard deviation 12.4); 14 were 70 years or older. Twenty-three had a previous cardiac operation and 22 had additional procedures performed at the time of double valve replacement. Before the operation 62% of the patients were in New York Heart Association functional class III and 29% were in class IV or required emergency operation. There were six (6.5%) deaths within 30 days. None of the hospital deaths were valve related; all occurred in patients who had additional risk concerns. Follow-up is 100% complete and ranges from 2 to 80 months, totaling 242 patient-years (mean 33.8 months). All except four hospital survivors reached class I or II and 40 patients (47%) remain asymptomatic. The actuarial survival rates are 82% at 1 year, 70% at 3 years, and 60% at 5 years. Causes of late death include heart failure (10), sudden, unexplained death (five), reoperation for coronary artery disease (one), noncardiac (four), and valve related (five). The linearized rate of fatal valve-related events is 2.1% pt-yr. A total of 22 valve-related complications (including five fatal) occurred is 18 patients, for a linearized rate or incidence of 9.1%/pt-yr. Eleven thromboembolic episodes (rate 4.6%/pt-yr) occurred in nine patients; three of these (1.2%/pt-yr) were fatal. Thromboembolic and bleeding complications represented 64% of all valve-related complications. Four patients had six episodes of prosthetic valve endocarditis (incidence 2.5%/pt-yr), of which one (incidence 0.4%/pt-yr) was fatal. Paravalvular leak contributed to the fifth valve-related death. At 5 years, 83% of patients were free of thromboembolic complications; 94% were free of anticoagulant-related hemorrhage; and 71% were free of all valve-related complications. There are few comparable data for patients who have had simultaneous replacement of aortic and mitral valves with other mechanical prostheses. The total incidence of valve-related complications for patients with bioprostheses ranges between 3.9%/pt-yr and 10.4%/pt-yr and is similar to the 9.1%/pt-yr observed in the present series. The type of valve-related complication (thromboemboli and bleeding versus valve deterioration) is the principal difference between St. Jude Medical and bioprosthetic valves in patients who require simultaneous replacement of aortic and mitral valves.

Thrombotic and bleeding complications of prosthetic heart valves

A review of articles published since 1979 indicates that thrombotic and bleeding complications account for about 50% of valve-related complications in patients with bioprosthetic aortic and mitral valves and for approximately 75% of the complications in patients with mechanical valves. Although compromised by lack of standard definitions and by variability in reporting and follow-up, the data suggest that the linearized rate of both thrombotic and bleeding complications in patients with aortic bioprostheses is approximately half that for aortic mechanical prostheses (2% versus 4%), but is approximately equal for both bioprostheses and mechanical valves in the mitral position (approximately 4%), and for mechanical and bioprosthetic aortic and mitral valves in combination. However, linearized rates for fatal thrombotic and bleeding events are two to four times higher in patients with mechanical prostheses. The adequacy of warfarin anticoagulation is the most important factor affecting thrombotic and bleeding complications in patients with mechanical valves and over shadows the dubious importance of other phenomena such as atrial fibrillation and left atrial thrombus. Short-term warfarin anticoagulation or the use of long-term platelet inhibitors, or both, do not appear to reduce the incidence of thrombotic complications in patients with aortic bioprostheses but increase bleeding. For mitral bioprostheses, the postoperative use of warfarin for three months or aspirin indefinitely is as effective in preventing thromboembolism as long-term warfarin. Acute prosthetic valve endocarditis is associated with a 13 to 40% incidence of thrombotic complications. Likewise, the recurrence rate of cerebral emboli is high (20-30%) in patients with prosthetic valves who are not anticoagulated. Bioprostheses are strongly preferred for women who wish to bear children; fetal wastage occurs in 25 to 30% of pregnant women with mechanical heart valves who receive either warfarin or heparin, or a combination of the two. Heparin, however, greatly increases the risk of maternal bleeding. In children, the efficacy of platelet inhibitors without warfarin anticoagulation is unproven; nearly all serious strokes occur when warfarin is omitted; and permanent disability from warfarin-related bleeding is rare. All prosthetic cardiac valves initiate coagulation and affect the dynamic equilibrium between activated procoagulants and endogenous anticoagulants. Warfarin is the only available oral exogenous anticoagulant.(ABSTRACT TRUNCATED AT 400 WORDS)

Bar calcification of the mitral anulus. A risk factor in mitral valve operations

Between Jan. 1, 1979, and Jan. 1, 1986, 72 septuagenarians had open heart operations for disease of the mitral valve. Thirty-two (44%) had additional operative procedures. Overall seven patients (9.7%) died within 30 days of operation. Eleven patients had bar calcification of the posterior mitral annulus as defined by three criteria and 61 did not. No differences between these two groups were present except for hospital mortality. Three of the 11 patients (27.3%) died at or soon after operation of complications resulting from the calcified annular bar. Only four of 61 patients (6.6%) without bar calcification died early. The difference in early mortality between the two groups is significant (p less than 0.05) and identifies the presence of bar calcification of the posterior mitral annulus as an independent risk factor of mitral valve operations in elderly patients.