Warren J. Taylor

Effects of Nitroglycerin on Regional Myocardial Blood Flow in Coronary Artery Disease

Regional myocardial blood flow before and after sublingual nitroglycerin was measured in 10 patients with coronary artery disease. During thoracotomy, (133)Xe was injected directly into the subepicardium in diseased regions of the anterior left ventricular wall, and washout rates were recorded with a scintillation counter. All disappearance curves were closely approximated by two exponential decays analyzed as two parallel flow systems by the compartmental method. The appearance of a double exponential decay pattern in diseased regions suggests that the slow phase was associated with collateral blood flow, although nonhomogeneous myocardium-to-blood partition coefficients for xenon cannot be excluded. Nitroglycerin increased the rapid phase flow in 9 of 10 patients and the slow flow in 7 of 10 patients. Average flow increased in 9 of the 10 patients (P < 0.01). Mean rapid phase flow in the control state was 110 ml/100 g per min and after nitroglycerin increased to 132 ml/100 g per min (P < 0.01); slow phase flow increased from 12 ml/100 g per min to 15 ml/100 g per min (P < 0.05). It is concluded that, under these conditions, nitroglycerin improves perfusion in regions of diseased myocardium in patients with coronary artery disease.

Aortic valve replacement with a gaged ball valve

Abstract 1. 1. Valve types and various materials are discussed. 2. 2. Skepticism is expressed regarding the durability of nonwettable cusps that must undergo double or triple flexion. 3. 3. Construction of ball valves in general is reviewed with specifications of this human aortic prosthesis. 4. 4. Fatigue, biologic and hydraulic testing devices are presented. 5. 5. Clinical results with two series of patients 1 year apart are reviewed in relation to technical problems and their solution. The problem of cardiac resuscitation has been greatly reduced by using moderate general body hypothermia, and profound local hypothermia to achieve cardioplegia. 6. 6. Late follow-up of patients 6 to 19 months after prosthetic replacement of the aortic valve is reported. The caged ball valve has been hemodynamically sound. There has been no evidence of damage to formed blood elements and no peripheral embolization. 7. 7. The ten cardinal features of prosthetic valves are defined.

A new therapeutic approach to acute coronary occlusion

Abstract 1. 1. A reproducible method for creating coronary occlusion with predictable and varied degrees of myocardial infarction in the closed chest animal is presented. 2. 2. Adjustment of microsphere dosage to animal body weight can provide animals suitable for study of the acute phase of coronary occlusion with high mortality or a preparation with myocardial infarction but long term survival suitable for the study of chronic coronary heart disease. 3. 3. Serum lactic dehydrogenase was observed to rise in all animals. The mean levels of response are directly related to microsphere dose and mortality. 4. 4. Two types of early death were observed in dogs that succumbed in 1 hour or less. Sixty per cent had shock followed by ventricular fibrillation in most cases. Forty per cent maintained an adequate blood pressure until ventricular fibrillation developed. Both mechanical failure and interruption of the normal conduction potential occurred in about equal proportions in the early deaths in this experiment. 5. 5. Electrocardiographic changes were inconsistent and sometimes transient in animals with proved disease at autopsy. 6. 6. Infarcts could be demonstrated in all dogs surviving 8 to 12 hours in this series. They closely approximated those in human subjects. Individual lesions could be found that were smaller than their human counterparts in those instances where coalescence of adjacent infarcts did not occur. 7. 7. Extracorporeal assisted circulation by arterioarterial counterpulsation has been previewed as a method of treating the early acute coronary occlusion.

Myocardial Blood Flow in Man: Effects of Coronary Collateral Circulation and Coronary Artery Bypass Surgery

The effects of coronary artery bypass graft (CAB) and coronary collaterals (CC) on myocardial blood flow (MBF) were studied in 24 patients undergoing 29 CABs. MBF after CAB was compared to preexisting MBF by intraoperatively injecting (133)xenon via distal CAB with proximal CAB first occluded then open. Pressure gradients across bypassed obstructions were measured. The results were correlated with preoperative coronary arteriograms to determine the effects of CC on MBF and postobstructive perfusion pressures. Mean MBF was increased by CAB from 32+/-6 (se) ml/min per 100 g (CAB occluded) to 118+/-13 ml/min per 100 g (CAB open). The (133)Xe clearance curves with CAB open were resolved into slow (19+/-2 ml/min per 100 g) and rapid (133+/-12 ml/min per 100 g) phases, suggesting that MBF remained heterogeneous after CAB. Vessels with less than 80% stenosis by angiography had pressure gradients less than 20 mm Hg across obstructions, high postobstructive perfusion pressures (75+/-7 mm Hg), and normal MBF (87+/-6 ml/min per 100 g) even with CAB occluded. Vessels with greater than 80% stenosis or total occlusion by angiography had significant pressure gradients with marked reduction of postobstructive MBF. No significant difference in postobstructive MBF was found when vessels with CC (21+/-4 ml/min per 100 g) were compared to those without CC (17+/-4 ml/min per 100 g) (P > 0.4). These studies demonstrate that (a) mean MBF increased 268% after CAB, (b) heterogeneous MBF persisted after CAB, (c) CC were not associated with significant increases in MBF, and (d) vessels with less than 80% stenosis had less than 20 mm Hg gradient with minimal effect on resting MBF.

Reoperation for Mitral Stenosis: A Discussion of Postoperative Deterioration and Methods of Improving Initial and Secondary Operation

A series of 80 reoperations for mitral stenosis in 79 patients is reported and analyzed. The most important causes of deterioration after valvuloplasty for mitral stenosis are inadequate initial operation, restenosis, and mitral insufficiency. Generally more than one of these factors pertain. An adequate mitral valvuloplasty requires the complete opening of both the anterior and posteromedial commissures and the mobilization of the chordae tendineae from each other and from the wall of the ventricle. The advantages and limitations of closed reoperation, open reoperation, the right-sided approach, and the use of the transventricular valvulotome are reviewed. More complete correction of stenosis with mobilization of posteromedial, anterior, and subvalvular chordae is emphasized. This is attained by operating from both the ventral and dorsal aspects of the patient through a left posterolateral thoracotomy incision. An Ivalon operating tunnel sutured to the left atrial wall at reoperation makes it possible to carry out the more extensive valvuloplasty at reoperations. A lower operative mortality, better longterm results, and fewer instances of deterioration are anticipated when this concept of improved valvuloplasty is effected initially.

Regional Myocardial Blood Flow

A method is described which measures the local effectiveness of the myocardial circulation, expressed as a clearance constant. Uniform clearance constants have been demonstrated in the normal canine and human myocardium. A distinct difference in clearance constants has been demonstrated between the normal canine myocardium and areas of naturally occurring disease. Heterogeneous clearance constants have been found in a majority of human subjects with coronary artery disease-the lowest rates being noted in areas of fibrous aneurysm.

The surgical correction of calcific aortic stenosis in adults: I. Technique of transaortic valvuloplasty∗

Abstract 1. (1) The life cycle of adults with calcific aortic stenosis is discussed. The ominous significance of left ventricular failure, even as manifested by dyspnea on exertion, is emphasized. 2. (2) A transaortic technique for the correction of this condition is presented. The substantial advantages of using a special Ivalon operating tunnel are reviewed. 3. (3) In the first 100 cases there have been 12 late deaths and 16 operative deaths. The operative mortality has been reduced to 5 in the last 60 consecutive patients. 4. (4) Eighty-six per cent of the surviving patients followed from 6 to 36 months are improved. 5. (5) The gratifying salvage from this fatal disease encourages further use of this method of surgical relief.

Internal Mammary Artery Implantation: Effect on Myocardial Lactate Utilization

Twenty-three subjects with angiographically documented coronary heart disease were studied by means of arterial and coronary sinus catheterization before and one year after internal mammary artery implantations. The pre- and postoperative patterns of lactate extraction at rest and after isoproterenol stress have been determined and correlated with clinical improvement and angiographic patency of the implant. In group I 13 subjects had implants that were angiographically seen to fill some portion of the coronary circulation. Eight of 11 who produced lactate preoperatively reverted to normal lactate extraction. Two extracted lactate at both studies. All but two had clinical improvement. No deaths occurred over a mean follow-up period of 40 months (range 20 to 64). In group II ten subjects bad implants with no visible connection to the coronary circulation. Only one subject had reversion of lactate production to extraction and two from extraction to production. Seven of ten did not improve clinically. Three deaths occurred over a mean follow-up period of 39 months (range 17 to 53). Agreement has been found between reversion to normal lactate metabolism, angiographic patency, and clinical improvement following internal mammary artery implantation.