Carolyn M. Conklin

Diffuse slow washout of myocardial thallium-201: a new scintigraphic indicator of extensive coronary artery disease

When coronary artery disease is extensive and of relatively uniform severity, regional myocardial hypoperfusion may be balanced during stress, precluding development of spatially relative perfusion defects. Assessment of the washout of thallium-201 from myocardial regions may provide diagnostic assistance in these cases because washout analysis is spatially nonrelative and hypoperfused myocardial regions manifest a slow thallium-201 washout rate. In 1,265 consecutive patients having quantitatively analyzed stress-redistribution scintigraphy, 46 had a diffuse slow washout pattern with no or a maximum of one regional perfusion defect. Thirty-two underwent clinically indicated coronary angiography, and 23 (72%) of these were found to have three vessel or left main disease. Of 30 similar patients without a diffuse slow washout pattern and with no or a maximum of one perfusion defect, only 5 (17%) had extensive coronary disease. An independent relation between diffuse slow washout and extensive coronary disease was demonstrated by a Mantel- Haentzel chi-square analysis of a wide variety of other indexes of extensive disease. A diffuse washout abnormality, even in the absence of other scintigraphic, clinical or electrocardiographic indicators, carries a high predictive value for three vessel or left main coronary artery disease. The predictive value is maintained when the exercise level achieved is submaximal. Although an infrequent occurrence (3.6% of tested patients), a diffuse slow washout pattern without other scintigraphic indications of extensive coronary disease should lead to further diagnostic testing.

CK-MB Release Following Coronary Artery Bypass Grafting in the Absence of Myocardial Infarction

Elevation of levels of the myocardial-specific isoenzyme of creatine kinase (CK-MB) in the immediate postoperative period in patients undergoing coronary artery bypass grafting is usually associated with myocardial necrosis. However, mean isoenzyme elevations of 18 +/- 2 IU/L (standard error of the mean) were recently observed in 6 patients in the absence of electrocardiographic or scintigraphic (technetium 99m stannous pyrophosphate) evidence of perioperative myocardial infarction. To test the hypothesis that surgical trauma of the atrium and aorta during cannulation for cardiopulmonary bypass might contribute to elevated CK-MB levels, biopsy of the right atrial appendage and aorta of 7 patients was done at operation, the tissue samples were assayed for total creatine kinase (CK) activity using the Rosalki technique, and for CK-MB using column chromatography. The results indicate that the human atrium is a rich source of CK, with the proportion of CK-MB similar to that present in the ventricle (20%). In addition, technical considerations inherent in the performance of coronary bypass surgery may result in release of CK-MB, causing elevated serum enzyme levels in the post-coronary artery bypass patient in the absence of myocardial infarction.

Fascicular conduction disturbances and ischemic heart disease: Adverse prognosis despite coronary revascularization

In patients with ischemic heart disease, fascicular conduction disturbances are associated with increased mortality. This study reveals that increased mortality also exists for certain types of fascicular conduction disturbances after myocardial revascularization. In 227 consecutive patients undergoing bypass surgery, 24 had preoperative and an additional 52 developed at surgery a fascicular conduction disturbance. At 66 +/- 14 months of follow-up, 6 (4%) of 148 control patients without pre- or postoperative fascicular conduction disturbances had died from cardiac causes. Although right bundle branch block and left hemifascicular block were the most common form of fascicular conduction disturbance, only 1 of 55 of these patients died (p = NS). Mortality rates were much higher for patients with left bundle branch block or an intraventricular conduction defect; 8 (38%) of 21 died from cardiac causes (p less than 0.05). A high risk subgroup was identified by comparing 14 consecutive patients with left bundle branch block or an intraventricular conduction defect who survived more than 1 year postoperatively with 21 consecutive patients with these same conduction defects who died within 1 year of surgery. The following variables were significantly (p less than 0.05) different (survivors versus nonsurvivors): age (58 +/- 7 versus 65 +/- 9 years); class IV angina (2 of 14 versus 16 of 21), prior myocardial infarction (9 of 14 versus 21 of 21), left ventricular ejection fraction (53 +/- 18 versus 41 +/- 15%), three vessel disease (9 of 14 versus 20 of 21) and left ventricular aneurysm (2 of 14 versus 13 of 21).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of protamine sulfate on myocardial oxygen supply and demand in patients following cardiopulmonary bypass.

The effect of protamine sulfate on myocardial oxygen supply and demand was studied under clinical conditions in nine patients following cardiopulmonary bypass. Before surgery, the patients had severe coronary artery disease with good ventricular function. The patients required no vasoactive drugs, but only blood volume adjustments when weaned off bypass, and were hemodynamically stable at the time of study. The protamine dose of 196 mg (2.5 mg/kg) was infused over 4 ± 1 minutes. Although modest variation in hemodynamic function occurred in individual patients after administration of protamine, there were no significant hemodynamic alterations for the group. No significant alteration in global myocardial metabolism was observed. Protamine caused a small decrease in measured coronary blood flow, resulting in a corresponding reduction in calculated myocardial oxygen consumption as coronary sinus oxygen content remained unaltered. Myocardial lactate extraction showed no significant alteration. It is concluded that protamine sulfate, given at rapid infusion rates in hemodynamically stable patients, is not associated with an adverse alteration in hemodynamics or global myocardial metabolism.

Cardiovascular effects of morphine in patients with coronary arterial disease.

Large doses of morphine sulfate have been reported to cause myocardial lactate production and reduction in coronary blood flow in animals. Similar effects with clinical doses in man would significantly alter the management of cardiac patients. Eleven adult patients with significant coronary arterial disease and normal left ventricular ejection fraction were studied before and 30 minutes after infusion of morphine (0.25 mg/kg IV). Evaluation of myocardial metabolism showed an increase in coronary sinus oxygen content (p < 0.001) and a reduction in myocardial oxygen consumption. Myocardial lactate extraction was not altered. No change in coronary sinus blood flow was seen. It is concluded that infusion of morphine sulfate, 0.25 mg/kg IV, does not produce global myocardial ischemia in patients with coronary artery disease and normal ventricular function.

Dobutamine and cardiac oxygen balance in patients following myocardial revascularization.

Dobutamine is frequently used in the early postoperative period following myocardial revascularization to improve cardiac output. Seven postoperative adult patients with low output syndrome were studied before and during intravenous dobutamine (mean ± SD: 5.1 ± 2.5 μg/kg/min) infusion. The metabolic effects were evaluated and related to hemodynamic changes. Cardiac index increased 40% (p < 0.05) with an increase in heart rate (p < 0.05) and decreases in systemic vascular resistance and right atrial pressure (p < 0.05). No significant changes occurred in arterial or pulmonary capillary wedge pressures or in stroke volume index. Dobutamine produced a 29% increase in myocardial oxygen consumption which, in these revascularized patients, was accompanied by a 35% increase in coronary blood flow. No significant alteration was observed in coronary sinus oxygen content or in global myocardial lactate extraction. Thus, despite the increased metabolic cost of dobutamine, global myocardial ischemia was not observed.

Role of intravenous verapamil in supraventricular tachyarrhythmias after open-heart surgery

Although the antiarrhythmic effects of verapamil (V) have been studied widely, its role in the treatment of atrial tachyarrhythmias after open-heart surgery (OHS) has not been defined. Accordingly, 22 patients were studied using a double-blind randomized crossover protocol 1 to 6 days after OHS, except for one patient, who was studied 90 days after OHS. Atrial fibrillation was seen in 18 and atrial flutter was observed in four patients. Two doses were used, 0.075 and 0.15 mg/kg (not exceeding 10 mg per dose), depending on the response. A positive response consisted of: conversion to sinus rhythm or heart rate less than 100 beats/minute (bpm). Eleven patients received V as the first drug; the remaining 11 received placebo first. Digoxin had been given to 20 patients (0.5 mg average dose) prior to inclusion in the study. Four patients converted to sinus rhythm within 30 minutes after V and one additional patient did so within 10 seconds of placebo administration. The post treatment heart rate combining both low and high dose response was 85 +/- 18 compared to 128 +/- 23 bpm for placebo (M +/- SD, p less than 0.01). The heart rate remained lower than control 30 minutes after V. Transient hypotension required intravenous fluid in one patient. Thus, V safely and rapidly controls heart rate but is not likely to result in immediate conversion to sinus rhythm in patients after OHS.

Adrenal function following coronary bypass surgery

Abstract Little is known about adrenocortical function after coronary bypass surgery in which moderate to deep hypothermia and cardiopulmonary bypass are used particularly with intraoperative steroid administration. Therefore, we performed a pilot study in which immediately preoperative and 18-hour postoperative serum cortisol levels were determined in eight patients who received 1.0 to 1.5 gm of methylprednisolone intravenously during surgery; postoperative serum cortisol (3 ± 1 μg%) levels were lower than preoperative levels (15 ± 3 μg%, p p p

Effects of calcium on the coronary and systemic circulation in patients after coronary surgery

Nine patients were studied three hours after aorto-coronary bypass. Before anaesthesia a radial arterial cannula was inserted and a thermodilution catheter placed into the pulmonary artery by fluoroscopy. A special thermodilution catheter was manipulated into the coronary sinus. Haemodynamic measurements were made plus cardiac output and coronary sinus blood flow. Content of oxygen and lactate in arterial and coronary sinus blood was determined. Series of measurements were done before and after 1 gm of CaCl2 given intravenously over 15 minutes. Calcium increased cardiac index and arterial pressure but not systemic vascular resistance. Total coronary sinus blood flow did not change, nor did myocardial oxygen consumption or coronary sinus oxygen content. Content of lactate in arterial and coronary sinus blood was unaltered and lactate extraction by the heart continued, in eight of nine patients. The improved haemodynamics were accomplished without inordinate risk to global ventricular energy metabolism.RésuméLe but de ce travail était de vérifier si les effets circulatoires bénéfiques du chlorure de calcium étaient obtenus au prix d’une augmentation de la consommation myocardique d’oxygène supérieure aux apports. A cette fin, neuf patients venant de subir un pontage aorto-coronarien ont été étudiés trois heures après leur arrivée aux soins intensifs.Avant l’induction de l’anesthésie, nous leur avions installé sous anesthésie locale une canule dans l’artère radiale et deux cathéters à thermodilution: le premier dans l’artère pulmonaire pour la mesure du débit cardiaque et le second placé sous fluoroscopie dans le sinus coronaire pour la mesure du débit sanguin dans le sinus coronaire (équivalent au débit de l’artère coronaire gauche).Les mesures suivantes ont été effectuées avant et après l’administration par voie intraveineuse, en quinze minutes, d’un gramme de chlorure de calcium: données hémodynamiques, débit cardiaque et débit du sinus coronaire, contenu en oxygène et en lactate du sang artériel et du sang prélevé dans le sinus coronaire.L’administration de chlorure de calcium élève le débit cardiaque et la pression artérielle, mais non la résistance vasculaire périphérique. Le débit du sinus coronaire ne s’est pas modifié, ni la consommation d’oxygène myocardique, ni le contenu en oxygène du sinus coronaire. Le taux des lactates dans le sang artériel et dans celui du sinus coronaire ne s’est pas modifié et l’extraction des lactates par le myocarde s’est continuée chez huit des neuf patients. Les effets bénéfiques sur la circulation se sont donc accomplis sans inconvénient pour l’équilibre énergétique du myocarde.

Effects of digoxin on myocardial oxygen supply and demand in patients following coronary artery bypass surgery.

Although digoxin is used frequently in patients in the prophylaxis of postoperative supraventricular tachyarrhythmias, the effects of the drug on myocardial oxygen supply and demand after coronary bypass have not been described. Seven adult patients with good ventricular function who underwent myocardial revascularization were studied before and three hours after digoxin (0.5 mg, iv). There were no significant changes observed in any measured systemic hemodynamic variable. Evaluation of global myocardial metabolism showed an increase in myocardial oxygen consumption (P < 0.05) which was compensated satisfactorily, as no significant alteration was noted in the coronary sinus oxygen content, or in the lactate gradient across the myocardium.Since the authors studied the effects of only one dose of digoxin, the effects of full digitalization in these patients remains to be defined.