Vasodilator drug effects on internal mammary artery and saphenous vein grafts.

The internal mammary artery is a dynamic conduit used for myocardial revascularization in which potential exists for spasm as well as for vasodilation. This study investigated vasodilator drug effects on the mammary artery using nitroprusside and nitroglycerin in vitro to measure the inhibition of contraction of human internal mammary artery and in vivo to examine blood flow through a canine mammary artery. In the in vitro study, ring segments of human internal mammary arteries were suspended on strain gauges in muscle baths containing 37 degrees C Krebs solution for measurement of isometric tension in vitro. Arterial contraction was stimulated with 70 mM potassium and 10 microM norepinephrine, and inhibition of contraction by vasodilators was measured. Nitroprusside was more potent and effective than was nitroglycerin in inhibiting potassium and norepinephrine contraction. The in vivo study utilized a canine (n = 8) right heart bypass preparation that allowed precise control of cardiac output, blood pressure and heart rate, which were maintained constant. The internal mammary artery graft and the saphenous vein graft perfused the same coronary artery bed. Electromagnetic flow probes measured graft flow (with the other graft occluded) before and after 15 min of drug infusion (1 microgram/kg per min). Nitroglycerin significantly increased mammary artery flow 36 +/- 13%, whereas nitroprusside significantly decreased it 12 +/- 2%. Saphenous vein grafts responded differently; graft blood flow decreased with nitroglycerin and increased with nitroprusside. Thus, although nitroprusside was more effective than nitroglycerin in inhibiting mammary artery contraction in vitro, it decreased internal mammary artery graft flow measured in vivo. Nitroglycerin had the opposite effect, increasing mammary graft flow.(ABSTRACT TRUNCATED AT 250 WORDS)

Importance of complete revascularization in performance of the coronary bypass operation.

Cardiac Data Bank records of 1,238 patients with triple-vessel disease (greater than or equal to 50% diameter reduction) who had undergone coronary bypass surgery were reviewed and divided into 2 groups depending on whether complete (n = 773) or incomplete (n = 465) revascularization had been accomplished. Patients with complete revascularization had a higher incidence of a normal preoperative electrocardiogram than did patients with incomplete revascularization (23 versus 14%, respectively, p less than 0.0001). The ejection fraction for both completely and incompletely revascularized patients was good (m = 0.60 and 0.57, respectively). The mean number of grafts per patient for the 2 groups was 3.8 and 2.6 (p less than 0.0001). There was no significant difference between the 2 groups with regard to postoperative inotropic requirements (8 and 7%), ventricular arrhythmias (1.8 and less than 1%), necessity for intraaortic balloon pumping (1.6 and 1.5%, hospital mortality (1.2 and 2.8%), or myocardial infarction (4.3 and 4.8%). Survival at 5 years was significantly greater (p less than 0.001) in patients with complete (88.5%) than in those with incomplete revascularization (83.5%). Reemployment occurred more often in patients with complete (52%) than in those with incomplete revascularization (40%) (p less than 0.001), and more patients were free of angina after complete (70%) than after incomplete revascularization (58%) (p less than 0.0005). Long-term survival appeared to be mediated primarily through improved revascularization rather than through differences in left ventricular function.

Propranolol therapy in patients undergoing myocardial revascularization.

The records of 185 consecutive patients having myocardial revascularization were reviewed with regard to preoperative administration of propranolol and intraoperative or postoperative complications. Tachycardia and hypertension before cardiopulmonary bypass were slightly more common in patients never taking propranolol or those who had discontinued it for more than 48 hours before operation. There was no statistically significant difference in the incidence of postbypass hypotension among patients who took propranolol within 24 hours of operation, those who discontinued it more than 24 hours before operation, and those who never took the drug. Operative mortality was not significantly different among patients who received propranolol within 48 hours of operation (3%), those who never took it and those who discontinued it more than 48 hours before operation (4%). Early in the series, five patients had an acute myocardial infarction within 48 hours after routine preoperative withdrawal of propranolol. Because complete withdrawal of propranolol in patients with unstable angina pectoris may lead to acute myocardial infarction, we recommend gradual withdrawal of the drug during 48 hours before operation. If this is not possible because anginal pain recurs or intensifies, then reduced doses may be given safely up to 10 hours before revascularization, provided that the patient is a satisfactory candidate for bypass and that adequate myocardial revascularization can be accomplished.

Aortic root dissection complicating coronary bypass surgery.

Four cases are presented of aortic root dissection after aortocoronary bypass surgery in which the origin of the intimal tear was at or very near the aortic site of saphenous vein anastomosis. Two cases were documented at autopsy. In one of two cases diagnosed with aortography, the patient underwent surgical correction and survived. All patients had long-standing severe hypertensive cardiovascular disease or severe generalized atherosclerotic disease, or both. Clinical awareness of aortic dissection after coronary bypass surgery in this group of patients should make early diagnosis with successful surgical correction feasible.

Value of coronary bypass surgery. Controversies in cardiology: Part I.

The value of coronary bypass surgery has been studied carefully during the last decade. Four methods, none perfect, have been used to compare the results of such surgery with the results of medical therapy. New data are likely to be merely supportive rather than the outcome of a definitive study with a new and a acceptable experimental design. It is therefore time to analyze the available data in light of the treacherousness of the disease and to determine if a clear trend is evident. There appears to be sufficient evidence to state that properly performed coronary bypass surgery will increase coronary blood flow and relieve angina pectoris in 90 percent of patients; total relief of angina can be expected in 60 percent and partial relief in 30 percent. Compared with modern medical therapy, properly performed coronary bypass surgery appears to prolong the life of patients who have obstruction of the left main coronary artery or triple or double vessel disease. There is not adequate evidence to state that the procedure will prolong the life of patients with single vessel obstruction. However, patients with single vessel obstruction and unacceptable angina pectoris should be considered for bypass surgery (especially patients with obstruction of the left anterior descending coronary artery). In practice, at Emory University Hospital, Atlanta, bypass surgery is recommended for young people with few symptoms if compelling obstructing lesions are present and in older patients only if their symptoms require it. Medical therapy is given before and after bypass surgery. When bypass surgery is performed in an excellent fashion (operative risk 1 percent) a great deal of "controversy" about this problem vanishes.

Coronary revascularization in the presence of ascending aortic calcification: use of an internal mammary artery-saphenous vein composite graft.

Complications arising from manipulation of the diseased ascending aorta constitute a significant portion of the morbidity and mortality of coronary revascularization. A case is described in which coronary revascularization was achieved by extension of the left internal mammary artery with a segment of reversed saphenous vein. The major advantage of this technique is that it obviates any instrumentation of the aorta or great vessels.

Physicians' assistants on a university cardiothoracic surgical service. A five-year update.

In 1973 two physicans' assistants (P.A.'s) were employed on a cardiothoracic surgical service at Emory University Hospital. In 1974 our initial experience with these paramedical personnel was presented to this Association. Since that time eight additional P.A.'s have been added to our service. They are now employed in four hospitals of the Emory University Woodruff Medical Center. New guidelines and regulations have been imposed at both the state and federal levels regarding P.A.'s, and their role in our center has become rather well defined. With over 1,700 cardiac cases and 600 thoracic cases per year to cover on our service, the P.A. has assumed a position of increasing importance both in operating room assistance and in preoperative and postoperative care. Since the university has maintained a constant number of residents and fellows during this interval, P.A.'s have filled needs of expanded clinical service in the various hospitals. In the pediatric and community hospitals associated with a university, the P.A. now functions as a junior house officer. In our university center, with a large resident staff, their role has become narrowed with definite guidelines. A Credentials Committee now governs the hiring of all P.A.'s by the University. When properly utilized and supervised, the P.A. can be a vital member of the cardiothoracic team. This report details our experience with P.A.'s for the past 5 years--culminating in a staff of ten P.A.'s working on our service in four types of hospitals within our university medical center.

A palliative operation for all types of aortic arch interruption in the neonate.

A palliative operation is described for the treatment of infants with all types of aortic arch interruption without regard to anatomic variation. It consists of establishment of continuity between the main pulmonary artery and descending thoracic aorta with a prosthetic graft, pulmonary artery banding distal to the graft, and ligation of the closing ductus arteriosus. Infant mortality rate in the past has been high, rega-dless of the type of operation used. The method of treatment described in this report is one in which an initial palliative operation is employed in the newborn period with total correction planned at a later date, when the risk of morbidity and death will be less.

Potassium-induced cardioplegia. Additive protection against ischemic myocardial injury during coronary revascularization.

Potassium-induced cardioplegia during anoxic arrest was utilized in a study of 190 consecutive patients undergoing revascularization (average 2.8 grafts per patient) from August, 1975, through August, 1976. Surgical technique, moderate systemic hypothermia with intermittent anoxic arrest, and the surgeon were the same for all patients. One hundred thirty-five patients (KC1-treated) received a bolus (150 ml.) of potassium solution injected into the proximal aortic root whenever the aortic cross-clamp was applied; 55 others served as control subjects. The mortality rate was 2.2% (three of 135) in the KCl-treated group and one of 55 in the control group. New Q waves appeared in 5.9% (eight of 135) of the KCl-treated patients and 11% (6 of 55) of control subjects (p = N.S.). Catecholamine drips were required after bypass in 4.4% (six of 135) of patients given potassium and 18% (10 of 55) of control patients (p less than 0.05). Profound myocardial relaxation was of added technical value with potassium. It is our impression that hearts treated with potassium exhibited more prompt cardioversion, separated from cardiopulmonary bypass with less need for inotropic support, and exhibited less myocardial injury during the revascularization procedure.

Inhibition of human internal mammary artery contractions. An in vitro study of vasodilators.

The internal mammary artery is currently the preferred conduit for myocardial revascularization; however, perioperative vasospasm of the internal mammary artery may limit its use as a bypass graft. The ability of various vasodilators to inhibit internal mammary artery contraction was investigated with the use of discarded segments of human internal mammary artery not used in coronary artery bypass grafting. Ring segments of human internal mammary arteries were suspended on strain gauges in muscle baths containing 37 degrees C Krebs solution for measurement of isometric tension in vitro. Arterial contraction was stimulated by elevating the extracellular potassium concentration to 70 mmol/L or by exposure to a 10 mumol/L concentration of norepinephrine, and inhibition of contraction by vasodilators was measured. The order of potency to inhibit potassium-induced contraction was as follows: nifedipine > verapamil > nitroprusside > papaverine. At maximal effective doses, nifedipine, verapamil, and papaverine almost completely inhibited potassium-induced contraction, whereas nitroprusside inhibited contraction by only 55%. When norepinephrine was used to contract the arteries, a biphasic relaxation curve was seen with nifedipine, but not with other vasodilator drugs. The order of potency to inhibit norepinephrine-induced contraction was as follows: nifedipine > nitroprusside > verapamil > papaverine. Maximal inhibition of norepinephrine contraction by these vasodilators ranged from 68% to 95%. Nitroglycerin, isoproterenol, and adenosine produced little or no inhibition of internal mammary artery contraction caused by potassium or norepinephrine. Although nifedipine was the most potent vasodilator, papaverine produced the greatest maximal inhibition of both potassium- and norepinephrine-induced contraction of human internal mammary artery.

Vasoactive drug effects on blood flow in internal mammary artery and saphenous vein grafts.

The internal mammary artery is a dynamic coronary graft, whereas the saphenous vein graft is passive. Therefore, potential exists not only for beneficial vasodilation but also for catastrophic spasm of the artery. The purpose of this study was to examine blood flow in the internal mammary and saphenous vein grafts during infusion of drugs that are commonly used after cardiac operations. A canine right heart bypass preparation allowed precise control of cardiac output, blood pressure, and heart rate, which were maintained constant during drug infusion. Both the internal mammary and saphenous vein grafts were constructed so that they perfused the same coronary bed: They were anastomosed in a Y fashion to a ligated anterior descending coronary artery. Electromagnetic flow probes measured graft flow (with the other graft occluded) before and after 15 minutes of drug infusion. The order of drug infusion was randomized and changes were compared by tests for paired differences. Phenylephrine (2 micrograms/kg/min) decreased flow in both the internal mammary and saphenous vein grafts, whereas norepinephrine (0.1 microgram/kg/min) increased flow in both grafts. Epinephrine (0.05 microgram/kg/min) increased mammary artery flow 16% +/- 6% but decreased saphenous vein graft flow 9% +/- 7%. Nitroglycerin (1 microgram/kg/min) significantly increased internal mammary flow (36% +/- 13%), from 47 +/- 7 to 59 +/- 7 ml/min (p less than 0.01), whereas flow decreased significantly in the saphenous vein graft 14% +/- 3%, from 64 +/- 9 to 59 +/- 8 ml/min (p less than 0.01). Nitroprusside (1 microgram/kg/min) decreased mammary artery flow 12% +/- 2%, from 50 +/- 7 to 44 +/- 7 ml/min (p less than 0.01), but increased saphenous vein graft flow 25% +/- 8%, from 64 +/- 9 to 77 +/- 7 ml/min (p less than 0.01). All hemodynamic variables were unchanged, except for norepinephrine, which significantly increased the first derivative of left ventricular pressure. The results suggest that flow through the canine internal mammary artery is changed by the drugs commonly used in perioperative management. Epinephrine and nitroglycerin increased internal mammary artery flow and decreased saphenous vein graft flow, whereas nitroprusside had the opposite effect. The vascular reactivity of the internal mammary artery must be considered when these drugs are used after coronary revascularization.

Pretreatment with lidoflazine, a calcium-channel blocker. Useful adjunct to heterogeneous cold potassium cardioplegia.

Ten mongrel dogs were studied to determine if pretreatment with lidoflazine would protect the canine myocardium during aortic cross-clamping when circumflex coronary artery occlusion limits the distribution of cold potassium cardioplegia. A canine right heart bypass preparation was used. Regional function was determined with a sonomicrometer. Twenty minutes before aortic cross-clamping, lidoflazine or solvent was administered in a random, blind fashion. A circumflex artery snare prevented the cardioplegic solution from entering the circumflex artery. A 100 minute arrest period with cardioplegic infusion every 20 minutes was followed by 45 minutes of reperfusion before global and regional function were reevaluated. In the group receiving solvent, postarrest function in the circumflex region recovered to only 30% of prearrest values (p less than 0.05), a marked functional deterioration. In the group protected by lidoflazine, function in the circumflex region returned to 90% of prearrest values (NS). Function in the left anterior descending (LAD) regions of both groups demonstrated full recovery after arrest. Global left ventricular function was well preserved in both groups and failed to reflect the damaged, malfunctioning region in the group receiving solvent. These findings suggest that pretreatment with lidoflazine can improve myocardial protection when delivery of cardioplegia is not homogeneous.

Alterations in regional myocardial function after heterogeneous cardioplegia.

Coronary stenoses lead to heterogeneous delivery of cardioplegic solution during cardiac operations. This situation was simulated by occlusion of the circumflex artery during cardioplegic infusion in canine right heart bypass preparations. Regional myocardial function (systolic shortening by sonomicrometer) was often diminished, despite preservation of global function. The correlation between recovery of circumflex regional function and recovery of stroke work or dP/dt (at constant aortic pressure, heart rate, and left atrial pressure) was poor (r = 0.17 and 0.07). The response of damaged regions to hemodynamic manipulations was studied. Increases in afterload after arrest did not lead to further deterioration of damaged regions. Volume loading (cardiac output 2 to 5 L/min) improved regional function even in severely damaged, bulging regions (p less than 0.05). Regional distensibility (delta length/delta left atrial pressure) decreased by 41% (p less than 0.02) in regions with poor protection and by 22% (p less than 0.01) in regions with good cardioplegic protection. There was also an increase in resting length (p less than 0.001) in both circumstances (5.2% and 3.7%). These changes in diastolic properties have not always been apparent in other experimental studies with less precise hemodynamic control. Heterogeneous cardioplegia causes heterogeneous changes in both diastolic distensibility and systolic function. These changes are poorly detected by examination of global ventricular function.

Further evaluation of the sutureless, screw-in electrode for cardiac pacing. Experience with first 300 implantations.

This report details our experience with 300 sutureless epicardial electrode implantations performed in the past 6 years. Indications for pacing, surgical approaches, implantation sites and complications are presented. The subxiphoid approach was valuable in obtaining safe, reliable, and long-term impulse generation. Complications have been few and of short duration. In general, pacing thresholds have been lower and sensitivity thresholds higher with left ventricular implantation than with right ventricular implantation. Endocarcial pacing is reserved for the very aged and debilitated patients, patients requiring implantation within 4 to 6 weeks of acute myocardial infarction, and for atrial or atrioventricular sequential pacing.

Cardioplegic infusion: the safe limits of pressure and temperature.

In patients with coronary artery disease, infusion of very cold cardioplegic solutions at elevated pressures may facilitate homogeneous cooling and cardioplegia. This study was designed to determine if very high infusion pressures or very low temperatures of the cardioplegic solution damages normal myocardium. In a hemodynamically controlled canine right heart bypass preparation, a crystalloid solution (Plasma-Lyte 148 with 30 mEq/L potassium chloride, 0 degree to 2 degrees C) was infused with separate control of the infusion pressures in the left anterior descending and circumflex arteries. A sonomicrometer measured regional myocardial function in each area. During a 100 minute arrest period, cardioplegic solution was reinfused every 20 minutes and reduced myocardial temperatures to an average of 9.4 degrees +/- 2.2 degrees C. In a comparison of infusion pressures of 50 versus 100 mm Hg and 100 versus 150 mm Hg, postarrest regional myocardial function was unchanged from prearrest. However, in a comparison of infusion pressures of 150 to 200 mm Hg, a significant fall in regional myocardial function was noted with the higher pressures (106% and 64% recovery, respectively, p less than 0.02, n = 6). Excluding the areas perfused at 200 mm Hg, comparison of regions cooled to less than 8 degrees C and to greater than 8 degrees C demonstrated no difference in recovery of regional myocardial function. In this study, elevation of cardioplegic infusion pressures to 150 mm Hg and lowering of myocardial temperatures to less than 8 degrees C caused no impairment of regional myocardial function.

An operation for relief of severe left ventricular outflow tract obstruction.

The case history of a 30-year-old man with severe mitral and aortic stenosis and slight aortic regurgitation who underwent replacement of both valves is presented. At the initial surgical procedure, because of the small-size annuli, a small Beall mitral prosthesis and a No. 19 Björk-Shiley aortic prosthesis were used. The subsequent recurrence of severe symptoms and findings of an 80 mm. Hg gradient across the Björk-Shiley aortic valve led to repeat exploration and corrective surgery. The operative procedure to relieve left ventricular outflow obstruction is described. It is felt that this procedure can be used not only for the relief of severe aortic annular stenosis but also for other forms of severe left ventricular outflow tract obstruction such as idiopathic hypertrophic subaortic stenosis and particularly in the patients who have experienced poor results with one of the known surgical procedures for this clinical entity.

Treatment of moderate mitral regurgitation and coronary disease by coronary bypass alone.

We have favored treatment of moderate mitral regurgitation and coronary disease with coronary bypass alone because of the high operative mortality of combined mitral valve replacement and coronary bypass. Between 1977 and 1983, coronary bypass alone was performed on 58 patients (mean age 63 +/- 8 years). Preoperatively, 90% had Canadian Cardiovascular Society class III or IV angina, and 10% had class III or IV congestive heart failure. In 72% mitral regurgitation had been caused by coronary disease. Hospital mortality was 3.4% (2/58). At follow-up (100% complete, mean 4.3 years) 66% of survivors were functional classes I and II (compared with 7% preoperatively, p less than 0.0001). Of those patients who worked preoperatively, 84% returned to work. There were no reoperations. The 5-year survival was 77%. In the same period combined mitral valve replacement and coronary bypass was required in 20 unmatched patients with moderate mitral regurgitation and coronary disease. Indications for valve replacement included congestive heart failure (10 cases), high left atrial pressure (three cases), and mitral stenosis (four cases). In these patients with more advanced symptoms the hospital mortality was 25%, and the 5-year survival was 31%. Treatment of moderate mitral regurgitation and coronary disease by coronary bypass alone achieved excellent hospital survival and long-term functional stability without a subsequent valve operation.

Hemangioma of the right ventricle causing outflow tract obstruction.

A 3 1/2-year-old child had a murmur of pulmonary stenosis. Echocardiography and cardiac catheterization revealed a pulmonary infundibular obstruction. Magnetic resonance imaging of the heart demonstrated a mass in the interventricular septum. The mass was successfully resected and a pathologic diagnosis of capillary hemangioma was made. Only two previous cases of hemangioma causing right ventricular outflow obstruction have been reported; both of these cases involved adults. This case represents the first report of a hemangioma causing right ventricular outflow tract obstruction in a child. An exploratory operation with resection is the treatment of choice.

Reoperation for prosthetic valve degeneration after Konno aortoventriculoplasty.

Since the introduction of the aortoventriculoplasty procedure by Konno in 1975, 16 patients have undergone aortic root augmentation by this method at the Woodruff Medical Center of Emory University. In four patients bioprosthetic valve degeneration 2 to 5 years after the Konno procedure has necessitated repeat operation and replacement of the prosthetic aortic valve. Modification of the septal patch or repeat right ventriculotomy has not been required. One patient required an additional lateral anulus-enlargement procedure (Manouguian) whereas the other three have demonstrated stability or growth of the aortic anulus. We have not observed recurrent subvalvular stenosis or problems with the right ventricular outflow tract. Repeat operation after aortoventriculoplasty has been relatively simple and has usually involved only the supra-annular aorta.

Aortic atresia and aortico-left ventricular tunnel: successful surgical management by Konno aortoventriculoplasty in a neonate.

A newborn infant with aortic atresia and aortico-left ventricular tunnel was successfully treated by Konno aortoventriculoplasty. A 15 mm Ionescu-Shiley pericardial xenograft was inserted when the patient was 5 days old and it was replaced with a 19 mm St. Jude Medical prosthesis at 2 years of age.