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Biomedical subjects

R J Gray

Publications and source records attributed to R J Gray.

At least 127 records · Page 7Linked to original sources
PubMed1983

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.

Aorta↗
PubMed1983

Thermodilution cardiac output determination in hypothermic postcardiac surgery patients: room vs ice temperature injectate.

In normothermic patients, room temperature and ice temperature injectate have been shown to result in comparable thermodilution cardiac output measurements. However, room temperature injectate may give inaccurate results in hypothermic patients, particularly if the injectate volume is small, because of the lower injectate-to-blood temperature differential. We compared determinations of cardiac output using 10- and 5-ml volumes of room temperature (19-25 degrees C) injectate to those using 10-ml volumes of ice temperature (0-5 degrees C) injectate in 26 hypothermic (32.7 +/- 1.2 degrees C) postcardiac surgery patients. The cardiac outputs ranged from 1.8 to 5.3 L/min. Regression analysis demonstrated a close relationship between the cardiac outputs measured using room temperature injectate compared to those using ice temperature injectate (0.951 for the 10-ml volumes, 0.925 for the 5-ml volumes). We conclude that the room temperature injectate method is acceptable for determining thermodilution cardiac outputs in moderately hypothermic patients.

Adult↗
PubMed1983

Coronary artery stenoses. Relationship between angiographic severity and impact on mean diastolic pressure gradient.

Coronary angiography provides important anatomic information about coronary artery stenoses. However, it is unclear whether specific assumptions about hemodynamic impact can be made from the angiogram. We therefore studied the relationship between angiographic severity of coronary stenoses and the mean diastolic pressure gradient measured directly at coronary bypass operation. We studied 29 stenoses selected because they were the only lesions in a given vessel, they were well seen in two angiographic views, and there was no change in clinical status of the patient between angiographic and surgical procedures. Fourteen stenoses were in the left anterior descending artery, nine were in the right coronary artery, and six were in the left circumflex artery. Correlation between mean diastolic gradient and percent stenosis was good (r = 0.78, p = 0.001) and especially so for lesions in the left anterior descending artery (r = 0.84, p = 0.001). Lesions over 90% had a wide range of gradients, while lesions less than 90% tended to have more predictable gradients. Collaterals invariably identified vessels with stenoses causing major pressure gradients. History of myocardial infarction was associated with major gradients in supplying vessels. Length of stenosis was not an important influence on gradient over a stenosis. We conclude that in some defined instances, generalizations about hemodynamic (and presumed functional) impact of stenoses can be made from the angiographic assessment, but precise assumptions are not possible.

Adult↗
PubMed1983

Arrhythmias and conduction disturbances following cardiac operation for the removal of left atrial myxomas.

Between September, 1971, and April, 1982, 11 patients (seven female) with left atrial myxomas underwent surgical resection at Cedars-Sinai Medical Center. The tumors ranged in size from 4 to 9 cm (mean 6.3 cm) and were attached to the interatrial septum (four superiorly, four inferiorly), the free atrial wall (one posteriorly, one at the dome), or both (one). Although all patients were symptomatic preoperatively, arrhythmias were uncommon; only one had chronic atrial fibrillation, and two others had had single episodes of paroxysmal atrial fibrillation in the immediate preoperative period. Early postoperatively, all but one patient had episodes of atrial fibrillation (eight patients), atrial flutter (four patients), junctional rhythm (six patients), sinus arrest (two patients), or complete heart block (three patients). Ten patients required antiarrhythmic therapy, and two required permanent pacemaker implantation. After a mean follow-up of 48 months (range 7 to 124), seven patients continue to have episodic or chronic supraventricular arrhythmias, with only three patients not using antiarrhythmic drugs regularly. The pathophysiological basis for these arrhythmias is unclear, but some patients appear to have sustained injury to the sinus node or atrioventricular node, while others have developed interatrial or intra-atrial conduction delays. Attention should be directed to the basis of these arrhythmias and conduction disturbances, as surgical technique may be the major determinant of this early and late postoperative complication.

Adult↗
PubMed1983

Transient hemodynamic dysfunction after myocardial revascularization. Temperature dependence.

We studied hemodynamics and the effects of right atrial pacing (110 beats/min) following complete myocardial revascularization and hypothermic multidose potassium crystalloid cardioplegia in 12 patients with a normal preoperative left ventricular ejection fraction (LVEF). Measurements were made immediately preoperatively, postoperatively at specified temperatures during the rewarming period (90 degrees F, 94 degrees F, and 98 degrees F), and at 24 hours. No patient had a perioperative myocardial infarction. At 90 degrees F, hemodynamics were characterized by significant decreases in cardiac index, stroke volume index, and left ventricular stroke work index (LVSW) and an increase in systemic vascular resistance index (SVRI) compared to preoperative values (p less than 0.05). Right atrial pacing significantly increased cardiac index preoperatively and 24 hours postoperatively, but not during the rewarming period. Over the entire rewarming period (90 degrees F to 98 degrees F), each of the following variables correlated with temperature: cardiac index (r = 0.71 in sinus rhythm and r = 0.66 with right atrial pacing); stroke volume index (r = 0.33 and 0.66); SVRI (r = -0.80 and -0.64); LVSW (r = 0.37 and 0.73); and heart rate in sinus rhythm (r = 0.51). During the rewarming period, there was an inverse relationship between cardiac index and SVRI (r = -0.87). In conclusion, after myocardial revascularization: (1) transient hemodynamic dysfunction occurs during the rewarming period (90 degrees F to 98 degrees F); (2) this dysfunction is temperature-dependent; and (3) right atrial pacing at 110 beats/min does not improve hemodynamic function during the rewarming period. Temperature must be considered in the evaluation of left ventricular and hemodynamic function following myocardial revascularization.

Adult↗
PubMed1982

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.

Blood Circulation↗
PubMed1982

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.

Adult↗
PubMed1982

Flow characteristics of the St. Jude prosthetic valve: an in vitro and in vivo study.

The St. Jude cardiac prosthetic aortic valve was evaluated in vitro and in vivo in an attempt to establish flow characteristics and to correlate them with clinical findings. In vitro, a fluid vehicle (6% Polyol V-10, 32 degrees C) with viscosity similar to blood (0.035 dyne-sec/cm2) was used under conditions of steady flow through a flow chamber simulating the aortic root. Gradient, velocity, and shear stress were measured 5.79 mm, 26.79 mm, 44.79 mm, and 77.79 mm downstream from 25-mm and 27-mm valves using a laser-Doppler anemometer. At 417 ml/sec, the valve gradient was 6.2 mmHg with the 25-mm valve, and 5.2 mmHg with the 27-mm prosthesis. Velocity was maximum at the orifice center, and wall shear stress was low (maximum 600 dyne/cm2). In vivo, six patients with 25-mm St. Jude aortic valves were studied within 48 hours after surgery to determine cardiac output, valve flow, and gradient. The gradient was 3.3 +/- 1.9 mmHg (M +/- SD) at 249 +/- 96 ml/sec and the effective valve area was as large as the geometric area (2.58 vs. 3.09 cm2). Thus, flow through the St. Jude valve is unobstructed and central, has low turbulence, and achieves optimal effective valve area for a given available orifice area.

Aortic Valve↗
PubMed1982

Membrane lipid alterations and thermal stress in Salmonella typhimurium 7136.

Salmonella typhimurium ATCC 7136 exhibited major changes in lipid composition when grown in the presence of either 0.15% sodium deoxycholate or 0.15% sodium benzoate. These lipophilic compounds had directly opposing effects on the lipid profile of the organism. The saturated/unsaturated ratio was markedly elevated in benzoate-grown cells. On the other hand, it was depressed by an even greater margin from the control after growth in the presence of deoxycholate. Adjustments in the phospholipid content of the cells were also recorded. Phosphatidylethanolamines decreased by 28 and 50% in the deoxycholate- and benzoate-grown cells, respectively. Compensatory increases in phosphatidylglycerols of 87.5 and 175% occurred, along with increases in cardiolipins of 12- and 22-fold, respectively. Deoxycholate or benzoate supplementation also altered the relative distribution of neutral lipids; again, benzoate stimulated the greater change. Compositional changes were accompanied in the organism by increased heat sensitivity, but the effect on the susceptibility of S. typhimurium to injury varied with the physical properties of the supplement used.

Benzoates↗
PubMed1982

Intravenous nitroglycerin and myocardial metabolism during anesthesia in patients undergoing myocardial revascularization.

Although intravenous nitroglycerin has been used to control the hypertensive response during sternotomy in patients undergoing myocardial revascularization, the effects of the drug on myocardial oxygen supply and demand have not been anesthetized for coronary artery bypass, were studied before and after administration of intravenous nitroglycerin (mean dose 12 microgram/kg in 6 minutes). Evaluation of myocardial metabolism showed an increase in coronary sinus oxygen content (p less than 0.05) and a reduction in myocardial oxygen consumption (p less than 0.05). Although mean myocardial lactate extraction and coronary sinus blood flow were not significantly altered in the group as a whole, variations in individual patient responses were observed and are discussed. These direct observations of global myocardial metabolism observed in this study group are similar to the conclusions reached by other investigators using indirect indices of myocardial oxygen supply and demand.

Anesthesia↗