Marjorie Raymond

Preoperative Prediction of Reversible Myocardial Asynergy by Postexercise Radionuclide Ventriculography

Myocardial asynergy is sometimes reversed by coronary bypass, and a noninvasive method of predicting which assess are reversible would be desirable. To assess whether changes in myocardial wall motion observed immediately after exercise can differentiate reversible from nonreversible myocardial asynergy, we evaluated 53 patients by radionuclide ventriculography before and after exercise and again at rest after coronary bypass surgery. Preoperative improvement in wall motion immediately after exercise was highly predictive of the surgical outcome (average chance-corrected agreement, 91 per cent). At surgery the asynergic segments that had improved after exercise were free of grossly apparent epicardial scarring. The accuracy of these predictions for postoperative improvement was significantly greater (P less than 0.01) than that of analysis of Q waves on resting electrocardiography (average chance-corrected agreement, 40 per cent). In contrast, preoperative changes in left ventricular ejection fraction after exercise were not predictive of postoperative resting ejection fraction. We conclude that postexercise radionuclide ventriculography can be used to identify reversible resting myocardial asynergy. This test should prove effective in predicting which patients with myocardial asynergy are most likely to benefit from aortocoronary revascularization.

Treatment of severe platelet dysfunction and hemorrhage after cardiopulmonary bypass: reduction in blood product usage with desmopressin.

Impairment of platelet function commonly occurs after cardiopulmonary bypass, and may result in substantial bleeding. Because desmopressin acetate (a synthetic analogue of vasopressin) shortens bleeding time in a variety of platelet disorders, a controlled clinical trial of intravenous desmopressin was performed in 39 patients with excessive mediastinal bleeding (greater than 100 ml/h) and a prolonged template bleeding time (greater than 10 minutes) more than 2 hours after termination of cardiopulmonary bypass. Twenty-three desmopressin recipients and 16 control patients (no desmopressin) were similar in surgical procedure, pump time, platelet count, template bleeding time and amount of bleeding before therapy (p = NS). Compared with the control group, the patients receiving desmopressin (20 micrograms; mean 0.3 micrograms/kg) utilized fewer blood products (29 +/- 19 versus 15 +/- 13 units/patient; p less than 0.05), especially platelets (12 +/- 9 versus 4 +/- 7 units/patient; p = 0.004), while achieving a similarly effective reduction in mediastinal bleeding (4.8- and 4.3-fold, p = 0.001 for both). Severe platelet dysfunction was partially corrected within 1 hour after desmopressin infusion, during which interval no blood products were administered: the template bleeding time shortened (from 17 to 12.5 minutes, p less than 0.05), whereas the platelet count remained unchanged (at 96 +/- 35 and 105 +/- 31 X 10(3)/mm3, p = NS). The plasma levels of two factor VIII components increased: procoagulant activity (VIII:C) from 0.97 +/- 0.43 to 1.52 +/- 0.74 units/ml (p less than 0.05) and von Willebrand factor (VIII:vWF) from 1.28 to 1.78 units/ml (p less than 0.05); these increases correlated with the shortening of the bleeding time (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Myocardial metabolism and hemodynamic responses to halothane or morphine anesthesia for coronary artery surgery.

Eighteen patients having coronary artery bypass grafts were randomly anesthetized with morphine (1 mg/kg) or halothane and oxygen. Central and peripheral pressures were measured serially, plus cardiac output and total coronary sinus blood flow, both by thermodilution catheters, starting before induction of anesthesia and continuing until completion of sternotomy. No significant differences in hemodynamic responses were seen between the two anesthetic techniques during induction: blood pressure and peripheral vascular resistance decreased significantly, but not cardiac output or coronary flow. Myocardial oxygen consumption decreased significantly with induction as oxygen content of coronary sinus blood increased, indicating preservation of oxygen balance. Heart rate and blood pressure increased after sternotomy in the patients given morphine, with the myocardium producing lactate in two of six patients and with nitroprusside being required in four patients to decrease arterial pressure. Halothane-oxygen anesthesia effectively controlled autonomic responses to sternotomy, although one of 12 patients had myocardial lactate production at that time. Neither rate-pressure product or ST segment changes were useful predictors of the ratio between myocardial oxygen consumption and supply. Myocardial oxygen balance can be maintained in coronary patients before cardiopulmonary bypass if pulse rate and blood pressure are kept at less than awake levels.

Nitrous oxide added to halothane reduces coronary flow and myocardial oxygen consumption in patients with coronary disease

The haemodynamic and myocardial metabolic effects of adding 50 per cent nitrous oxide to 0.5 per cent halothane were studied in 13 patients, before the surgical incision for coronary artery vein grafts. Cardiac output and coronary sinus blood flow were determined by thermodilution, along with haemodynamic measurements. Measurements 15 minutes after addition of nitrous oxide revealed a significant decrease in heart rate, arterial pressure, cardiac index, coronary sinus blood flow and myocardial oxygen consumption. There was a significant increase in coronary sinus lactate content, and a significant decrease, from 27 to 11 per cent, in myocardial lactate extraction. We conclude that these circulatory changes were likely to be due to a depression of ventricular function by the nitrous oxide. The myocardia of these patients with severe coronary disease were becoming globally ischaemic while they were receiving 50 per cent oxygen, in the presence of hypotension. Nitrous oxide should be turned off when hypotension occurs in coronary patients.RésuméLes effets métaboliques et hémodynamiques myocardiaques ont été observés en ajoutant 50 pour cent de protoxyde d’azote à 0.5 pour cent d’halotane à 13 patients avant I’incision chirurgicale de la grqffe de l’artère coronaire. Le débit cardiaque et le débit sanguin du sinusal coronaire furent déterminés avec la technique de thermodilution suivie de mesures hémodynamiques. Les mesures obtenues 15 minutes après l’addition de protoxyde d’azote ont démontré une baisse significative de la fréquence cardiaque, de la pression artérielle, de l’index cardiaque, du débit sanguin du sinusal coronaire et de la consommation de l’oxygèlne myocardiaque. On observa une hausse significative du contenu lactate du sinusal coronaire et une baisse significative de 27 à H pour cent, de l’extraction lactate myocardique. En conclusion, ces variations circulatoires doivent être causées par une dépression de la fonction ventriculaire par le protoxyde d’azote. Les myocardies de ces patients souffrant de graves malaises coronaires développèrent une ischémie coronairienne durant ia piriode où Us recurent 50 pour cent d’oxygène, alors qu’ils étaient hypotensifs. Le protoxyde d’azote ne devrait pas être administré lorsque l’hypotension est présente chez des malades souffrant de malaises coronaires.

Effects of intubation on coronary blood flow and myocardial oxygenation

Effects on haemodynamics and myocardial oxygenation of endotracheal intubation were examined in 17 patients after halothane induction and 12 after I mg · kg-1 of IV morphine. Six patients having each anaesthetic were pretreated with IV propranolol (0.1 mg · kg-1) 45 minutes earlier. Arterial and intracardiac pressures, cardiac output and total coronary sinus blood flow (CSBF), both by thermoditution, were determined plus arterial-coronary differences of oxygen, haemoglobin and lactate. Blood pressure (BP), heart rate and CSBF were recorded continuously during intubation. The subjects were candidates for coronary bypass grafts, but had good ventricular function (mean ejection fraction 0.68 ± 0.13 SD).From their reduced levels after induction, BP, cardiac index and systemic vascular resistance increased to awake levels following intubation. Mean CSBF in non-betablocked patients increased to awake level along with BP. More myocardial oxygen was extracted and consumed after intubation, but lactate extraction continued: these data are evidence of adequate oxygen supply. Induction with either halothane or morphine effectively prevented the hypertensive response to intubation. Acute beta blockade led to less increase in heart rate from intubation.RésuméLes effets de l’intubation endotrachéale sur l’hémodynamique et l’oxygénation myocardique ont été examinés chez 17 patients après induction à l’halothane et chez 12 patients après administration intraveineuse de 1 mg · kg-1 de morphine. Six patients ayant reçu l’un ou l’autre des agents anesthésiques ont été pré-traités avec du propranolol IV (0.1 mg·kg-1) 45 minutes au préalable. La pression artérielle ainsi que les pressions intracardiaques, le débit cardiaque ainsi que le flot sanguin total du sinus coronaire (CSBF) tous les deux par thermodilution, ont été déterminés. Il en est de même pour les différences d’oxygène entre le contenu artériel et le contenu du sinus coronaire. L’hémoglobine ainsi que le lactate ont été mesurés. La pression artérielle (BP). la fréquence cardiaque et le CSBF ont été enregistrés continuellement lors de l’intubation. Les sujets étaient des candidats à des pontages aorto-coronariens mais avaient une bonne/onction ventriculaire (fraction d’éjection moyenne 0.68 ± 0.13 SD).Après leurs valeurs réduites post-induction, la tension artérielle, l’index cardiaque et la résistance vasculaire systémique ont augmenté à des valeurs identiques à celles de l’état de réveil post-intubation. Le CSBF moyen chez les patients non bêta-bloqués a augmenté à des niveaux identiques aux valeurs à l’ état de réveil. Il en est de même pour la tension artérielle. Plus d’oxygène myocardique a été extrait et consommé après l’ intubation, mais l’extraction de lactate a continué, indiquant que l’apport d’oxygène était adéquat. L’induction avec les deux agents a empêché efficacement la réponse hypertensive à l’intubation. Le blocage bêla aigu des patients a amené moins d’augmentation de la fréquence cardiaque lors de l’intubation.

Transient appearance of Q waves in coronary disease during exercise electrocardiography: Consideration of mechanisms and clinical importance

Myocardial ischemia occurring during exercise may be manifested electrocardiographically by transient depression or elevation of the ST segment or by increases in the R wave amplitude.’ Transient Q waves in this setting are unexpected, in that Q waves generally indicate evolving myocardial infarction (MI). We are therefore reporting the case of a patient with severe coronary artery disease (CAD) in whom Q waves not associated with MI developed transiently during an exercise stress test, in order to consider the possible mechanisms and clinical implications of this unique phenomenon. Exemplary patient. A 72-year-old Caucasian male was referred to the nuclear stress testing laboratory for evaluation because of mild exertional angina, recently progressive in severity. On examination, he was thin and muscular. The resting heart rate (HR) was 48 bpm and the resting BP was 160/80 mm Hg. The physical examination was within normal limits. Resting ECG revealed sinus bradycardia with firstdegree heart block (Fig. 1, top panel). The patient exercised for 11 minutes according to the standard Bruce protocol treadmill test, achieving a maximal HR of 126 bpm. At 10 minutes of exercise, at a HR of 115 bpm and BP of 140/90, he developed chest tightness that gradually increased in severity. At 11 minutes of exercise, there was a 20 mm Hg drop in systolic BP, and for this reason exercise was terminated. The standard 12-lead ECG obtained immedi-

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.