John L. Pennock

Aortic valve replacement and combined aortic valve replacement and coronary artery bypass grafting: predicting high risk groups

To determine which groups of patients are at highest risk for operative or late mortality, 259 consecutive patients who underwent operation between 1978 and 1984 were studied; 170 underwent aortic valve replacement and 89 underwent aortic valve replacement combined with coronary artery bypass grafting. Multivariate analysis of risk factors selected emergency operation and patient age older than 70 years as the strongest predictors for operative death. Although patients having aortic valve replacement and coronary artery bypass grafting had a higher operative mortality rate (13.5 versus 3.5%), the combined operation had no independent predictive effect on early or late results. At a mean follow-up time of 48 months after surgery, 72% of the survivors of operation were living, 10% were lost to follow-up and 18% were dead. Seventy-seven percent of long-term survivors were in New York Heart Association functional class I or II. The incidence of thromboembolism, paravalvular leak, bacterial endocarditis and hemorrhage each occurred at a rate of less than 1% per patient-year. The factors associated with late death were preoperative age, male sex, left ventricular end-diastolic pressure, cardiac index and functional class. Despite an increase in operative mortality, patients undergoing emergency operation were not at higher risk of late death. Operative mortality is concentrated among several high risk groups. For patients undergoing elective operation, operative mortality is low, especially if the patient is less than 70 years old. Late results are good for all groups of patients undergoing operation, including those who are at greater risk of dying at operation.

Delayed reversal of impaired vasodilation in congestive heart failure after heart transplantation.

The effects of changes in central cardiovascular function on peripheral vasodilation were investigated. Strain gauge plethysmography was used to measure the maximal blood flow response following release of forearm arterial occlusion and the peak reactive hyperemic blood flow response (ml/min.100 ml) before and twice after orthotopic heart transplantation in 10 subjects with severe congestive heart failure. The 2 posttransplantation studies were done before hospital discharge (mean 18 days after transplantation) and again after discharge (mean 114 days after transplantation). Transplantation led to a significant but delayed increase in maximal vasodilation (reactive hyperemic blood flow: pretransplant 21 +/- 3; predischarge 25 +/- 2; postdischarge 43 +/- 5) and a concurrent significant reduction in minimal forearm resistance. Although the improvement in peripheral vasodilator function may be linked to improvement in cardiac function, this linkage is not direct, nor is it immediate. If the normalization of maximal metabolic blood flow is related to resumption of normal physical activity postdischarge, then much of the basic abnormality in vasodilator capacity in congestive heart failure may be related to physical deconditioning.

Survival and Complications Following Ventricular Assist Pumping for Cardiogenic Shock

Thirty patients (pts) have undergone ventricular assist pumping for up to 25.4 days (mean 6.8 days). Twenty-eight pts could not be weaned from cardiopulmonary bypass (CPB) after open heart operations and two pts sustained myocardial infarctions (MI), with cardiogenic shock unresponsive to medical therapy previous to surgery. Twenty-two pts required left ventricular assistance (LVA); 55% (12/22) were weaned from the pump and 32% (7/22) survived. Two pts required right ventricular assistance (RVA); both were weaned from the pump and survived. Six pts required right and left ventricular assistance (BVA) and none survived. Postoperative survival for program years 1976 through 1979 (14 pts) was 14% (2/14). Postoperative survival for program years 1980 through 1982 (16 pts) was 44% (7/16), reflecting improved pump insertion techniques (left atrial cannulation) and pt management. Since 1980, 12 pts have required LVA, nine have been weaned from the pump, and six pts have survived (50%). One pt has required RVA and has survived, and three pts requiring BVA did not survive. Seven pts have been alive and well 5, 9, 14, 19, 24, 30 and 36 months after surgery. Five are NYHA functional Class I status and two pts are NYHA Class II status. Current data indicates that single ventricular assistance in pts who cannot be weaned from CPB is “reasonable and therapeutic treatment to extend life.”

Reduction of myocardial infarct size: comparison between left atrial and left ventricular bypass.

A controlled study was undertaken to quantitate and compare the effect of left ventricular bypass (LVB) and left atrial bypass (LAB on left ventricular infarct volume (LVIV). After baseline studies, the left anterior descending coronary artery in each of 30 mongrel dogs was ligated 1-1.5 cm from its origin. After baseline ischemic studies, control dogs (group 1--10 dogs), LAB dogs (group 2--10 dogs), and LVB dogs (group 3--10 dogs) were monitored for four hours. Final infarct size was determined by the nitroblue tetrazolium staining technique. Heart rate, mean arterial pressure, and total systemic flow (TSF) showed no significant difference between control and left heart bypass groups. In group 1, the LVIV was 27.7 +/- 6.5 g/100 g left ventricle (LV). In group 2, left heart bypass (LHB) flow was 90 +/- 4% of TSF. The pressure time index (PTI) was 2845 +/- 52 mm Hg-sec/min. The PTI demonstrated no significant difference from cntrols. In group 2, LVIV was 22.5 +/- 6.0 g/100 g LV. LVIV was reduced 18.8% from controls (p less than 0.08). In group 2, LHB was complete. Left ventricular decompression (group 3) resulted in a PTI of 328 +/- 76 mm Hg-sec/min. The PTI was significantly different (p less than 0.001) from groups 1 and 2. The LVIV was 12.6 +/- 5.1 g/100 g LV. LVIV was reduced 54.5% from controls (p less than 0.001) and 44.0% from group 2 (p less than 0.001). These results suggest that LVB may be useful, not only in supporting the circulation in the patient with myocardial infarct and cardiogenic shock, but also in limiting infarct size.

Risks of Mitral Valve Replacement and Mitral Valve Replacement with Coronary Artery Bypass

One hundred thirty consecutive patients who underwent mitral valve replacement (MVR) or MVR with coronary artery bypass grafting (CABG) using cold crystalloid cardioplegic solution were analyzed to determine operative mortality and risk factors. Twenty-eight patients had mitral stenosis (MS), 37 had mitral regurgitation (MR), 37 had mixed MS and MR, 23 had MR with coronary artery disease (CAD), and 5 had MS with CAD. Preoperative pulmonary artery pressure, pulmonary capillary wedge pressure, and cardiac index were not different among groups, but patients with MR and CAD had a significantly higher left ventricular end-diastolic pressure (LVEDP) and a significantly lower ejection fraction than other groups. Mortality was 7.1% for patients with MS, 5.4% for MR, 8.1% for mixed MS and MR, 0 for MS with CAD, and 21.7% for MR and CAD. Overall mortality was 9.2%. Eleven patients had emergency operations for cardiogenic shock with a mortality of 45%. Nineteen additional patients in New York Heart Association (NYHA) Functional Class IV had MVR or MVR plus CABG with a mortality of 26%. Sixteen patients required intraaortic balloon pump assistance, and 9 survived. Four patients with MR and CAD required the left ventricular assist device, and 3 survived. Excluding patients who had emergency operations, overall mortality was 5.8%. Excluding patients who had emergency operations and patients in NYHA Functional Class IV, overall mortality was 2%. Factors associated with death were cardiogenic shock, NYHA Class IV, LVEDP greater than 15 mm Hg (16% mortality), and age greater than 60 years (15% mortality).

Strut Fracture and Disc Embolization in Bjork-Shiley Mitral Valve Prostheses: Diagnosis and Management

Mechanical failure of the Björk-Shiley tilting disc prosthesis is a rare but catastrophic complication of the valve. Several previously reported cases of major strut fracture with disc embolization led to improvements in the structure of the prosthesis. A case of minor strut fracture in the improved convexoconcave model of the Björk-Shiley mitral valve prosthesis is described. The literature on mechanical failures in the Björk-Shiley mitral valve prosthesis is reviewed, and recommendations for recognition and management of this problem are made.

Perioperative Management of Drug Therapy

Patients with cardiovascular disease presenting for surgery require meticulous perioperative management of all drugs they are receiving, so that complications of drug-anesthesia interaction and drug toxicity are prevented. The therapeutic strategy for drugs such as diuretics, cardiac glycosides, propranolol, and nitrates is presented.

The artificial heart: implantation technique.

Gradual improvements in artificial heart design and fabrication, combined with the use of established principles of clinical cardiac surgery, now permit uniform survival of calves following artificial heart implantation. The development of our current operative technique is based on a successful experience with cardiac valve replacement in the calf. Tricuspid valve replacement performed through a right, fifth interspace thoracotomy provides an excellent opportunity to verify anesthetic and cardiopulmonary bypass (CPB) techniques similar to those required during artificial heart implantation. Once routine survival has been achieved following tricuspid valve replacement, the team is ready to undertake artificial heart implantation. This paper describes our current technique used to implant the pneumatic powered angle port design artificial heart (Figure 1) in calves.