Ronald M. Becker

Application of transesophageal echocardiography to continuous intraoperative monitoring of left ventricular performance

Transesophageal M mode echocardiography was used for continuous monitoring of left ventricular dimensions in 21 patients (11 with valvular and 10 with coronary heart disease) undergoing open heart surgery. Echocardiograms were recorded in six stages of the procedure and simultaneous measurements of cardiac output (with dye dilution) and atrial pressures were made. Measurements of left ventricular diameters with the transesophageal technique correlated excellently with the corresponding measurements obtained with the standard parasternal method. In patients with volume overload, surgical correction was accompanied by a decrease in diastolic dimension, velocity of circumferential fiber shortening, mid wall stress and end-diastolic stiffness, and an increase in cardiac output. Pericardial and chest wall closures generally caused a significant decrease in cardiac output, and correlated with a decrease in diastolic diameter and an increase in the stiffness constant of the left ventricle. Thus, the decrease in cardiac output may have been due to decreased distensibility of the ventricular cavity secondary to mechanical restriction by the pericardium and chest wall. Pericardial opening caused a significant delay in septal motion that was reversed by closing the pericardium. This study confirms the validity of transesophageal echocardiography and its usefulness in monitoring changes in ventricular function during cardiac surgery.

Intracardiac Surgery in Pregnant Women

A survey of members of The Society of Thoracic Surgeons was undertaken to obtain information on experiences with cardiac operations in pregnant women. The experiences reported were highly successful, with only 1 maternal death in 68 procedures utilizing cardiopulmonary bypass and more than 80% survival of fetuses. Cardiac operations in pregnant patients probably can be made safer by avoidance of perfusion hypothermia and by use of fetal heart and uterine monitoring. When valve replacement is necessary, use of biological valves is recommended to avoid the necessity for anticoagulation.

Mechanism of reduction of mitral regurgitation with vasodilator therapy

Acute mitral regurgitation was produced in six open chest dogs by excising a portion of the anterior valve leaflet. Electromagnetic flow probes were placed in the left atrium around the mitral anulus and in the ascending aorta to determine phasic left ventricular filling volume, regurgitant volume and stroke volume. The systolic pressure gradient was calculated from simultaneously measured high fidelity left atrial and left ventricular pressures. The effective mitral regurgitant orifice area was calculated from Gorlins hydraulic equation. Infusion of nitroprusside resulted in a significant reduction in mitral regurgitation. No significant change occurred in the systolic pressure gradient between the left ventricle and the left atrium because both peak left ventricular pressure and left atrial pressure were reduced. The reduction of mitral regurgitation was largely due to reduction in the size of the mitral regurgitant orifice. Reduction of ventricular volume rather than the traditional concept of reduction of impedance of left ventricular ejection may explain the effects of vasodilators in reducing mitral regurgitation.

beta-Blockade therapy for supraventricular tachyarrhythmias after coronary surgery: a propranolol withdrawal syndrome?

A high incidence of cardiac arrhythmias and hypertension has been noted after coronary artery bypass surgery in patients previously treated with oral propranolol. Forty-two patients undergoing coronary bypass surgery had propranolol withdrawal 10 hours before surgery and were randomized into a group treated with propranolol immediately postoperatively, and a nontreatment group. Patients treated with prophylactic propranolol had a significantly lower incidence of postoperative supraventricular arrhythmias compared to patints who received no prophylaxis. All the arrhythmias responded rapidly to 1 mg of intravenous propranolol therapy, whether it was used as a primary treatment or as a supplement to prophylactic propranolol. The findings suggest that (1) there is a high incidence of supraventricular arrhythmias and sinus tachycardia after coronary artery bypass which might reflect an abrupt propranolol withdrawal, and (2) that perioperative prophylactic or supplementary propranolol therapy will successfully prevent or treat most of these arrhythmias.

Clinical pharmacology of the new beta-adrenergic blocking drugs. Part 10. Beta-adrenoceptor blockade and coronary artery surgery

Abstract In an attempt to resolve the controversy concerning propranolol therapy in patients undergoing coronary artery revascularization surgery, 54 consecutive patients with stable angina pectoris receiving chronic propranolol therapy entered a randomized trial and were compared with 17 patients on no propranolol therapy (group I). The 54 patients were divided into three treatment groups: in group II (n = 17) propranolol was abruptly withdrawn 48 hours prior to surgery, in group III (n = 18) propranolol was abruptly withdrawn 10 hours prior to surgery, in group IV (n = 19) propranolol was maintained until the day of surgery, half the usual dose was given 2 hours prior to surgery, and intravenous propranolol was administered every four hours postoperatively. Patients in group II and III had significantly higher increases in the rate-pressure product (RPP) during intubation, and in the postoperative periods compared to patients in groups I and IV. Group IV had the lowest increase in RPP during intubation and a significantly lower incidence of postoperative supraventricular arrhythmias. Patients abruptly withdrawn from propranolol, at 10 or 48 hours preoperatively, are more prone to increments in myocardial oxygen demands than those patients not treated with propranolol postoperatively or who were maintained on the drug. Plasma renin activity, although lower in patients treated with propranolol (group IV), did not seem to play a role in the RPP increments seen. The increased sympathetic tone associated with intubation and the postoperative period most likely contribute to the increments in RPP and the increased incidence of arrhythmia. These data show that (1) propranolol may be given safely to patients at the time of coronary artery bypass and may be maintained postoperatively without a decrement in left ventricular performance; (2) there is a “rebound effect” or increased sympathetic activity in patients who have propranolol abruptly withdrawn 10 or 48 hours prior to surgery. This “rebound effect” causes a marked increase in myocardial oxygen demands during intubation and the postoperative periods, with an increased incidence of arrhythmias. (3) Continuous propranolol treatment up until the time of surgery with maintenance of intravenous therapy in the immediate postoperative period provides protection against these complications. (4) The data and implications can reasonably be expected to apply to propranolol-treated patients with angina pectoris undergoing general anesthesia and noncardiac surgical procedures.

Noncardiogenic pulmonary edema and peripheral vascular collapse following cardiopulmonary bypass: rare protamine reaction?

Four instances of severe anaphylactoid reaction occurring subsequent to cardiopulmonary bypass are described. These catastrophic reactions, from which 2 patients died, took place approximately an hour following administration of protamine and were characterized by marked peripheral vasodilatation, loss of capillary membrane integrity, and fulminant noncardiogenic pulmonary edema. Primary cardiac depression was not evident. We hypothesize that protamine was the causative agent in these unusually severe reactions. Differential diagnosis from other causes of acute cardiorespiratory dysfunction depended on early assessment of pulmonary artery and left ventricular filling pressures, cardiac output, respiratory mechanics, and arterial blood gases. Therapy was difficult; success in 1 of the patients seemed to have been effected in part by prompt administration of high-dose corticosteroids and maintenance of peripheral vascular tone with an alpha-adrenergic agonist.

Medium-Term Follow-up of the Ionescu-Shiley Heterograft Valve

Utilizing a questionnaire specifically designed to uncover potential thromboembolic episodes, we personally interviewed 97 patients who underwent valve replacement with the Ionescu-Shiley valve between January, 1977, and June, 1980. In both the aortic and mitral positions, the attrition rate after the first year was low; cumulative survival at 3 to 4 years was 78% (aortic) and 61% (mitral). None of the deaths were attributed to primary valve failure. Patients with aortic prostheses, none of whom were anticoagulated, had a cumulative thromboembolism-free rate of 94% at 3 to 4 years. Patients with mitral prostheses had a thromboembolism-free rate of 71% at 3 to 4 years with 80% of the episodes occurring in patients in atrial fibrillation. Most emboli produced only transient symptoms, and only 1 patient has residual impairment. The Ionescu-Shiley valve performs well in the early years after valve replacement. Anticoagulation should be strongly considered for patients with mitral prostheses who are in atrial fibrillation.

CORTISOL AND ANTIDIURETIC HORMONE RESPONSES TO STRESS IN CARDIAC SURGICAL PATIENTS

The hormonal responses to anaesthesia and cardiac surgery were studied in patients undergoing valve or coronary bypass surgery. Marked increases in antidiuretic hormone levels as a result of surgical stress were seen, and were of approximately equal magnitude in both groups. Although both groups also showed marked increases in plasma cortisol levels in response to operations, this response appeared to be relatively blunted in valve surgery patients, especially at the end of operation and in the intensive care unit. This blunted cortisol response may be a manifestation of exhaustion of adrenocortical reserves in valvular surgical patients whose sympathoadrenal system has already been chronically stimulated by a low output state.The important role of the neuroendocrine system in maintaining homeostasis postoperatively has long been recognized; this relative cortisol deficiency may be aetiologically related to poor postoperative recovery in critically ill valvular surgery patients.RéSUMéLes réponses hormonales à l’anesthésie et à la chirurgie ont fait l’objet de la présente étude effectuée chez un groupe de malades soumis à une chirirgie valvulaire ainsi que chez ceux d’un second groupe subissant une chirurgie coronarienne. On a observé une élévation marquée de 1’hormone anti-diurétique secondaire au stress de la chirurgie et cette élévation était semblable chez les patients des deux groupes. Le taux du cortisol s’est également élévé chez les patients des deux groupes en réponse au stress chirurgical, mais cette réponse était atténuée chez les valvulaires, en particulier en fin d’intervention et dans la phase postoperatoire immédiate. Une telle réponse chez les valvulaires peut refiéter l’epuisement des réserves adreno-corticales chez des patients dont le système adreno-sympathique a été stimulé de façon chronique par la présence d’un bas débit cardiaque.Le rôle important du systéme neuro-endocrinien dans le maintien du l’homoéostase post-opératoire est connu depuis longtemps; la déficience relative en cortisol peut contribuer ç une évolution post-opératoire difficile chez des patients en condition critique.

Pressure-Flow Relations and Energy Losses Across Prosthetic Mitral Valves: In Vivo and In Vitro Studies

The use of the Gorlin equation (1) to estimate the area of a prosthetic mitral valve has received widespread acceptance despite frequently questionable results. We have found, for example, that intra-operative studies on patients undergoing valve replacement with mitral bioprostheses sometimes yield exceptionally small valve areas during low cardiac output states. This study was designed to analyse the pressure-flow relations across prosthetic mitral valves and to determine the in vivo conditions which would lead to inaccurate area calculations when using the Gorlin equation.