Samuel V. Lichtenstein

Warm heart surgery and results of operation for recent myocardial infarction

Revascularization procedures after recent myocardial infarction are associated with higher mortality and morbidity compared with elective coronary artery bypass grafting. Traditional methods of myocardial protection impose a further ischemic insult on already compromised myocardium. Continuous cold blood cardioplegia may eliminate ischemia but may still leave the heart anaerobic. Theoretically, warm aerobic arrest addresses both of these issues and may become an attractive alternative to standard hypothermic ischemic arrest in this setting. In 115 nonrandomized patients undergoing coronary artery bypass grafting within 6 hours to 7 days of an acute myocardial infarction, myocardial protection was provided with continuous cold (4 degrees C) or continuous warm (37 degrees C) blood cardioplegia. Fifty-one patients (after 1988) protected with warm blood cardioplegia were compared with a historical cohort of 64 patients (before 1988) protected with cold blood cardioplegia. Results indicate that the warm cardioplegia group had no mortality versus 10.9% for the cold group (p less than 0.05), a myocardial infarction rate of 2.0% in the warm versus 9.3% in the cold group, and use of intraaortic balloon pump of 0% versus 12.5%, respectively (p less than 0.05). It is concluded that continuous warm aerobic arrest may minimize ischemia and anaerobic metabolism during the operative procedure, and may be of benefit to patients who have a limited tolerance to ischemic insult.

Technical aspects of warm heart surgery

Abstract Intermittent hypothermic cardioplegia has been adopted as the method of choice for myocardial protection by most surgeons. The most important aspect of this protection is believed to be adequate hypothermia. An alternative technique has been developed, based on the principles of electromechanical arrest and normothermic aerobic perfusion using continuous warm blood cardioplegia. With this method of myocardial protection the heart is maintained at 37°C throughout the operative procedure. The specific technical aspects used shall be described in detail.

Cardiovascular Effects of Positive Pressure Ventilation in Humans

Pulsus paradoxus is the pathological exaggeration of the normal transient decrease in arterial blood pressure that occurs during spontaneous inspiration. The transient increase in arterial pressure associated with positive pressure inspiration is termed reversed pulsus paradoxus (RPP). Cardiorespiratory interactions and the mechanism of these effects have been studied extensively in animals, and to a lesser extent, in humans. In this clinical investigation pulsus paradoxus and RPP were studied in 10 postoperative cardiac patients with invasive monitoring and mediastinal pressure catheters placed intraoperatively. From end-expiration to end-inspiration, RPP was accompanied by decreased transmural pressures in the right atrium, left atrium, and aorta. Left ventricular end-systolic volume measured by radionuclide studies diminished during a positive pressure inspiration, without a significant change in end-diastolic volume. These results are consistent with decreased left ventricular afterload as the major mechanism of RPP. During spontaneous breathing, inspiration was associated with converse effects, a fall in arterial pressure and an increase in transmural right atrial, left atrial, and aortic pressures from end-expiration to end-inspiration. End-systolic volume was significantly larger at end-expiration than end-inspiration, with no change in end-diastolic volume. These findings suggest that an increase in left ventricular afterload during inspiration is responsible for the observed pulsus paradoxus.

Operation for acute postinfarction mitral insufficiency using continuous oxygenated blood cardioplegia

Patients with acute-onset mitral insufficiency and cardiogenic shock after myocardial infarction have a high incidence of operative death and morbidity. Patients with ventricular dysfunction, myocardial ischemia, and limited cardiac reserve undergoing an urgent operation represent a challenge to modern methods of myocardial protection. To improve results of operation a new technique was devised with continuous infusion of cold oxygenated blood cardioplegia during the entire cross-clamp period. Between 1984 and 1988, 19 consecutive patients with severe mitral regurgitation and cardiogenic shock (systolic blood pressure less than 60 mm Hg) after myocardial infarction underwent urgent myocardial revascularization, mitral valve replacement, or both. Left ventricular ejection fraction was less than 40% in 16 of 19 patients. All patients had suffered myocardial infarction within 4 weeks of operation and underwent an urgent operation within 24 hours of the onset of hemodynamic compromise. Severe three-vessel coronary artery disease was present in 16 of the 19 patients. A continuous infusion of blood cardioplegia was instituted at aortic cross-clamping and continued throughout the cross-clamp period. Infusion of continuous blood cardioplegia was also instituted through each completed distal vein graft. Myocardial septal and left ventricular apical temperatures were maintained at 10 degrees +/- 2 degrees C throughout the cross-clamp period. There were two in-hospital deaths (mortality, 10.5%) and low output syndrome was present in 10 patients (53%). At a mean follow-up of 2.5 years, there was one late death and 14 of the 16 remaining patients were in New York Heart Association functional class I or II.(ABSTRACT TRUNCATED AT 250 WORDS)

Modified cabrol shunt for control of hemorrhage in repair of type A dissection of the aorta

A technique of modifying the Cabrol shunt using preserved bovine pericardium and a patch of autologous pericardium to deal with postoperative hemorrhage from an ascending aortic operation is described. A fistula to the right atrium was created for autotransfusion. This simple technique is very useful for dealing with the catastrophic complication of such postoperative hemorrhage.

A Simple Model of Right Ventricular Hypertrophy

Previous models of right ventricular hypertrophy (RVH) created by pulmonary artery (PA) banding in adult large animals have been associated with an unpredictable response of the right ventricle to the band and a high mortality due to the variable degree of acute stenosis. We studied the efficacy of PA banding in young pigs to produce RVH by progressive gradual stenosis during growth. Sixteen Yorkshire pigs at 6 weeks of age had nonconstricting 5-mm wide Dacron strips placed around the PA via a left minithoracotomy. The animals were returned for study in 2-3 months. There were no deaths during the growth period. Five sham-operated pigs acted as controls. Right ventricular free wall (RVFW) to total heart weight ratio was greater in the banded group (0.38 +/- 0.05 vs. 0.28 +/- 0.01, P less than .005) as was the RVFW to left ventricular free wall (LVFW) weight (1.09 +/- 0.25 versus 0.66 +/- 0.03, P less than .005). While the LVFW to total heart weight ratio decreased (0.36 +/- 0.04 vs 0.45 +/- 0.05, P less than .005), the septal ratio did not change (0.26 +/- 0.04 vs. 0.29 +/- 0.02, NS), indicating concomitant septal hypertrophy. This technique is simple, reliable, and reproducible in creating right ventricular and septal hypertrophy in the young pig with no mortality during maturation.

Systemic vascular effects of epinephrine administration in man

Although the peripheral vascular effects of epinephrine have been characterized in animal models, similar studies have not been carried out in man. To determine the vascular effects of epinephrine the systemic circuit must be conceptually and surgically opened to allow for independent control of flow and pressure. This unique situation exists in man only while on total cardiopulmonary bypass with an external reservoir and pump interposed between the right atrium and the aorta. Under these conditions, peripheral vascular compliance, arteriolar and venous resistance, and the systemic time constant (a measure of the drainage characteristics of the vascular bed, in units of time) can be determined directly. Nine anesthetized patients undergoing normothermic cardiopulmonary bypass were studied before and during epinephrine infusion (5 micrograms/kg/min) after the aorta was cross-clamped and the heart had been isolated from the rest of the peripheral circulation. At constant blood flow epinephrine infusion increased blood pressure and reservoir volume (effectively decreasing blood volume) by an average of 360 ml. Although systemic vascular compliance decreased (due to venoconstriction), resistance to venous return decreased. Analysis of transient blood volume changes after a step change in right atrial pressure at constant blood flow revealed that blood was effectively draining from two vascular compartments with different time constants, as previously demonstrated in animal experiments. Epinephrine caused redistribution of blood flow away from the compartment with the longest time constant by constricting the arterioles leading to it. This accounts for the major increase in venous return and is almost entirely the mechanism of increased cardiac output in the normal individual after its administration, independent of its effects on the heart. In an attempt to localize the long and short time constant vascular compartments, three normal volunteers were studied. Thallium-201 whole body imaging at rest and after maximal treadmill exercise showed redistribution of blood flow away from the mesenteric bed and towards the muscle compartments. Although two similar compartment models of the circulation have been suggested by others, to our knowledge this type of analysis has not been carried out in man.

Myocardial protection in the hypertrophied right ventricle

Hypertrophied right ventricle presents a sensitive state that may not be adequately protected by modern cardioplegic methods. Cardiac metabolism, performance, and ultrastructure were measured in response to 1 hour of cardioplegic arrest in 15 pigs with right ventricular hypertrophy using intermittent hypothermic crystalloid, blood, and Flusol DA 20%-based cardioplegia. Reperfusion time was 1 hour. One hour after a 60-minute cross-clamp period, there were no differences in light microscopy. Total energy stores increased in 4 of 5 animals given blood cardioplegia compared with 1 of 5 for each of the other groups. Cardiac performance data also showed better results for animals treated with blood cardioplegia. After 30 minutes of reperfusion, animals receiving blood cardioplegia recovered 131% +/- 42% of preoperative systolic performance compared with 106% +/- 49% for Fluosol-treated animals and only 82% +/- 27% recovery for the crystalloid-treated group. After 60 minutes of reperfusion, the blood group showed 119% +/- 20% recovery compared with 89% +/- 23% and 85 +/- 50% recovery for Fluosol- and crystalloid-treated hearts, respectively. In conclusion, blood cardioplegia provided better protection than did crystalloid or Fluosol DA 20% cardioplegia when animals with right ventricular hypertrophy underwent 1 hour of cardioplegic arrest. It may have repaired damaged myocardium, leaving better hearts after cross-clamping than before.

Visceral and Limb Perfusion During Thoracoabdominal Aortic Aneurysm Repair

Patients undergoing thoracoabdominal aortic aneurysm repair are at high risk of operative morbidity and death. Aortic clamping and unclamping stresses the myocardium, interrupts visceral and limb perfusion, and leads to metabolic acidosis. Use of a simple technique to preserve distal perfusion during the period of aortic clamping may reduce perioperative morbidity. We describe a technique of visceral and limb perfusion that may reduce surgical risk in high-risk patients.

Study on myocardial contractility after cardiopulmonary bypass versus cardioplegic arrest in an air-ejecting in vivo heart model

Cardiac function was assessed in a working in vivo canine heart preparation. Minute work and myocardial oxygen consumption (MVo2) were measured after a two-hour period of hypothermic hyperkalemic crystalloid cardioplegic arrest in one group of dogs (Group 1, N = 6) and in another group of dogs on cardiopulmonary bypass (CPB) alone (Group 2, N = 6). Results indicate that at an afterload of 50 cm H2O, minute work was the same in all hearts but MVo2 was significantly higher in Group 1 hearts at all levels of preload. At higher afterloads, both minute work and MVo2 were significantly greater in Group 1 hearts over the range of preloads tested. Ventricular compliance was decreased in Group 1 over the range of preloads studied. These results suggest that hearts undergoing cardioplegic arrest had better left ventricular contractility than hearts undergoing CPB alone.