Biomedical subjects

A K Jabr

Publications and source records attributed to A K Jabr.

7 recordsLinked to original sources

PubMed1990

Continuous warm blood cardioplegia: a new technique for myocardial protection.

Hypothermia is used to prolong the safe period of ischemic arrest by reducing the heart's oxygen demands. Due to this effect, hypothermia has been the fundamental component of most methods of myocardial protection during cardiac surgery. However, hypothermia has a number of unwanted side effects, such as detrimental effects on enzyme function, energy generation, and cell membranes. Since electromechanical arrest accounts for 90% of myocardial oxygen consumption, arresting the heart with chemical cardioplegia will reduce O2 consumption dramatically. Therefore, if the resting (arrested) heart is continuously perfused with oxygenated blood cardioplegia, one can easily provide the remaining 10% of O2 that it requires. Under these conditions, the need for hypothermia becomes questionable. In this paper, we describe the perfusionist's experience using the antegrade and retrograde technique of continuous warm blood cardioplegia.

Blood↗

PubMed1986

A physiological approach to surgery for acute rupture of the papillary muscle.

There is controversy regarding the optimal management of patients in whom acute papillary muscle rupture develops. This study evaluates the effect of division of the anterolateral papillary muscle on left ventricular (LV) function and compares two methods of treatment--mitral valve replacement (MVR) and mitral valve repair. Thirteen pigs were placed on cardiopulmonary bypass, and interventions were performed in an isolated beating heart preparation. LV function was assessed with a compliant intraventricular balloon at baseline, after division of the anterolateral papillary muscle (Divided), after repair of the divided papillary muscle (Repair), and finally after MVR. Division of the anterolateral papillary muscle caused a significant deterioration in LV function. Function was maintained at this level after mitral valve repair but deteriorated with MVR. Developed pressure measured at baseline was 179 +/- 13 mm Hg; Divided, 148 +/- 11 mm Hg (p less than 0.05 versus baseline); Repair, 149 +/- 15 mm Hg; and MVR, 95 +/- 8 mm Hg (p less than 0.05 versus Divided) at a balloon volume of 20 ml. These results suggest that LV function is impaired by papillary muscle rupture. Repair of the ruptured papillary muscle is associated with better LV function than is MVR.

Acute Disease↗

PubMed1986

Toward a better understanding of the etiology of left ventricular dysfunction after mitral valve replacement: an experimental study with possible clinical implications.

The relatively high morbidity and mortality of mitral valve replacement (MVR) appears to be related to an impairment in left ventricular (LV) function. This two-part investigation was designed to assess the effect of MVR on global LV function in an isolated heart preparation and to evaluate whether a mitral prosthesis with a flexible annulus would be of benefit. In Part I (14 pigs), the effects of each step in MVR were studied. Division of the chordae tendineae caused a severe deterioration in LV function (systolic pressure, 180 +/- 13 versus 120 +/- 10 mm Hg; p less than 0.05; developed pressure, 167 +/- 13 versus 108 +/- 11 mm Hg; p less than 0.05; first derivative of LV pressure [dP/dt], 2,630 +/- 300 versus 1,610 +/- 180 mm Hg/sec; p less than 0.05; balloon volume, 30 ml). Fixation of the mitral annulus prior to division of the chordae tendineae resulted in a small decrease (not significant) in LV function but had no effect after the chordae tendineae were divided. In Part II (10 pigs), two mitral annular prostheses were studied: a standard rigid prosthesis and a prosthesis of identical size but with a flexible annulus. LV function was better with the flexible than the rigid prosthesis (systolic pressure, 118 +/- 10 versus 89 +/- 5% control, p less than 0.02; developed pressure, 120 +/- 11 versus 87 +/- 5% control; p less than 0.02; dP/dt, 119 +/- 10 versus 85 +/- 4% control; p less than 0.02; balloon volume, 30 ml).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1986

The effects of cardioplegic arrest on right atrial function.

Atrial electrical and mechanical activity persists during cardioplegic arrest. It has been postulated that atrial ischemia may occur and cause deterioration in atrial function. This study was designed to assess the effect of cardioplegic arrest on right atrial function. Twenty-one pigs were placed on cardiopulmonary bypass (CPB), and the right atrium was isolated from the circulation by snaring both venae cavae and incising the coronary sinus. The tricuspid valve was closed through a small right ventriculotomy, and baseline atrial function was assessed using a compliant balloon in the atrium. Fourteen pigs underwent one hour of cardioplegic arrest (7 with cardioplegia alone [CCA group] and 7 with the addition of topical hypothermia [CCA + TH group]) followed by one hour of normothermic reperfusion. Seven other pigs were placed on CPB for the same period of time (CPB group). Atrial electrical and mechanical activity persisted at 45 beats per minute in the CCA group but was virtually abolished in the CCA + TH group. Cardioplegic arrest caused considerable deterioration in right atrial function (developed pressure, 18.9 +/- 0.8 [baseline] versus 14.1 +/- 0.7 mm Hg; p less than 0.05; first derivative of atrial pressure [dP/dt], 187 +/- 19 versus 134 +/- 25 mm Hg per second; p less than 0.05; 60 minutes of reperfusion and balloon volume of 20 ml). It was not affected by topical cooling. Right atrial developed pressure was maintained, but dP/dt was significantly reduced in the CPB group. This study suggests that cardioplegic arrest does not protect the atrium.

Animals↗

PubMed1986

A rational approach to the selection of an assist device for the failing right ventricle.

Assist devices have become available for the treatment of right ventricular (RV) failure. The present study assesses the efficacy of pulmonary artery balloon counterpulsation (PABC) in restoring RV output to normal levels. In a porcine model of RV failure during left heart bypass, PABC restored RV output to normal, provided that the RV output was not depressed to less than 50% of baseline values. When RV failure was more severe, PABC was not effective in restoring RV output to base line. This study suggests that a rational approach should be developed for the use of right heart assist devices. In moderately severe RV failure, PABC may be successful in restoring cardiac output to normal. However, in extreme failure a right heart bypass is necessary.

Animals↗

PubMed1985

Is atrial function affected by conventional cardioplegic arrest?

Conventional cardioplegic arrest results in persistent atrial electrical and mechanical activity. This activity has been postulated to result in atrial ischemia which can induce postoperative arrhythmias and impair the transport function of the atrium. In this study, the effects of simple cardiopulmonary bypass (CPB) (seven pigs) and conventional cardioplegic arrest (CCA) (seven pigs) on right atrial function were evaluated. Function was assessed in an isolated right atrial preparation with a compliant balloon inserted via the superior vena cava. CCA for 1 hr produced significant deterioration in right atrial function (developed pressure 14.1 +/- 0.7 vs 18.9 +/- 0.8 mm Hg, P less than 0.05, diastolic pressure 10.0 +/- 1 vs 4.5 +/- 1.4 mm Hg, P less than 0.05, dP/dt 134 +/- 25 vs 187 +/- 19 mm Hg/sec, P less than 0.05 at a balloon volume of 20 ml after 1 hr of reperfusion). CPB alone caused no alteration in pressures in the right atrium but was associated with a late decrease in dP/dt (developed pressure 19.3 +/- 1.8 vs 18.9 +/- 0.8 mm Hg, diastolic pressure 4.0 +/- 1.2 vs 4.5 +/- 1.4 mm Hg, dP/dt 148 +/- 18 vs 187 +/- 19, P less than 0.05 at a balloon volume of 20 ml at a time corresponding to 1 hr of reperfusion in the CCA group). These results are consistent with the postulate that conventional techniques of cardioplegic arrest are associated with ischemic dysfunction of the right atrium.

Animals↗

PubMed1985

The hemodynamic effects and mechanism of action of pulmonary artery balloon counterpulsation in the treatment of right ventricular failure during left heart bypass.

The efficacy of pulmonary artery balloon counterpulsation (PABC) was evaluated in improving right ventricular (RV) output during left heart bypass for global cardiac failure. In 13 pigs, a 40-ml balloon was positioned within a graft anastomosed to the pulmonary artery distal to the pulmonary valve, and left heart bypass was instituted from the left atrium to the carotid artery. Global myocardial failure was produced by an infusion of propranolol (range, 25 to 78 mg). In this model, RV output decreased despite volume loading to a right atrial pressure of 15 mm Hg and atrioventricular sequential pacing at 100 beats per minute. Pulmonary artery balloon counterpulsation increased both RV output (from 519 +/- 76 to 1,117 +/- 110 ml/min; p less than 0.01) and RV systolic stroke work (from 1.3 +/- 0.4 to 2.3 +/- 0.6 gm-m; p less than 0.01). Right atrial pressure decreased (from 15.5 +/- 0.9 to 10.7 +/- 1.0 mm Hg; p less than 0.01) in 8 of the pigs studied during RV failure. In 5 pigs, ventricular fibrillation occurred without a stable model of RV failure, and there was no cardiac output before or after counterpulsation. The mechanism of action of PABC was studied by placing a flow probe around a large branch of the right pulmonary artery. During RV failure, balloon inflation caused flow through the pulmonary circulation, and ventricular systole resulted in filling of the graft. During ventricular fibrillation, balloon inflation and deflation produced only a to-and-fro movement of blood in the pulmonary artery branch without net forward flow.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗