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Biomedical subjects

J Ivanov

Publications and source records attributed to J Ivanov.

At least 109 records · Page 6Linked to original sources
PubMed1985

A comparison of nitroglycerin and nitroprusside: I. Treatment of postoperative hypertension.

Nitroglycerin improves perfusion to ischemic myocardial regions and therefore has theoretical advantages over sodium nitroprusside to treat hypertension (mean arterial pressure [MAP] greater than 95 mm Hg) following coronary bypass operation. Thirty-three hypertensive patients were randomized to an initial infusion of either nitroglycerin or nitroprusside in a crossover trial designed to reduce MAP to 85 mm Hg. Thermodilution cardiac output measurements permitted calculation of left ventricular stroke work index (LVSWI), and nuclear ventriculograms permitted estimation of left ventricular ejection fraction, left ventricular end-diastolic volume index (LVEDVI), and left ventricular end-systolic volume index (LVESVI). Coronary sinus blood flow was measured by the continuous thermodilution technique, and arterial and coronary sinus lactate measurements permitted calculation of myocardial lactate flux (MVL). Both nitroglycerin and nitroprusside reduced MAP (-25 +/- 12 mm Hg and -20 +/- 10 mm Hg, respectively; not significant [NS]). Nitroglycerin reduced LVSWI more than did nitroprusside (-15 +/- 13 gm-m/m2 and -7 +/- 9 gm-m/m2, respectively; p less than 0.01). Both agents increased left ventricular ejection fraction (nitroglycerin, +8 +/- 8%, and nitroprusside, +10 +/- 7%; NS), and decreased LVEDVI (-20 +/- 22 ml/m2 and -11 +/- 17 ml/m2, respectively; NS) and LVESVI (-13 +/- 14 ml/m2 and -10 +/- 12 ml/m2, respectively; NS). Coronary sinus blood flow decreased with both drugs (NS), but MVL increased with nitroglycerin (+0.02 +/- 0.14 mmol/min) and decreased with nitroprusside (-0.02 +/- 0.02 mmol/min) (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Output↗
PubMed1985

A comparison of nitroglycerin and nitroprusside: II. The effects of volume loading.

The treatment of postoperative hypertension with nitroglycerin or nitroprusside reduces cardiac filling, and volume loading is required to maintain hemodynamic and metabolic stability. Postoperative hypertension (mean arterial pressure greater than 95 mm Hg) developed in 33 patients who were randomized to an initial infusion of nitroglycerin or nitroprusside in a crossover trial. Volume loading (a rapid infusion of 250 to 500 ml of colloid to raise the left atrial pressure 2 to 4 mm Hg) was instituted prior to hypertension and again following the crossover trial during the infusion of nitroglycerin (11 patients) and nitroprusside (13 patients). Volume loading increased left ventricular end-diastolic volume index (LVEDVI) as documented by nuclear ventriculography, cardiac index (CI), and left ventricular stroke work index (LVSWI). Although CI was higher (p less than 0.01) with nitroprusside at any level of LVEDVI, myocardial performance (the relation between LVSWI and LVEDVI) was not different. Diastolic compliance (the relation between left atrial pressure and LVEDVI) was increased (p less than 0.01) with nitroglycerin. Myocardial metabolism was assessed by calculating myocardial lactate flux (MVL), the product of myocardial lactate extraction and coronary sinus blood flow by the thermodilution technique. Volume loading increased MVL during nitroglycerin therapy and decreased (p less than 0.01) MVL during nitroprusside therapy. Volume loading restored preload and increased CI with both nitroglycerin and nitroprusside. Only nitroglycerin improved myocardial lactate utilization. Nitroglycerin is the preferred vasodilator when ischemia is suspected after coronary bypass operations.

Cardiac Volume↗
PubMed1985

Hemodynamic and myocardial metabolic consequences of PEEP.

The cardiac effects of positive end expiratory pressure (PEEP) were examined in 50 patients six hours after elective coronary bypass surgery. Increasing the level of PEEP from 5 to 10 to 15 cm H2O decreased cardiac index (evaluated by thermodilution), stroke index and left ventricular end diastolic volume index without a change in left ventricular ejection fraction (evaluated by nuclear ventriculography). Right ventricular end diastolic volume index remained unchanged. Coronary sinus blood flow (measured by the continuous thermodilution technique) and myocardial oxygen and lactate consumption were unchanged with the application of 15 cm H2O PEEP. In 21 patients, volume loading (250 ml [mL] of plasma) was performed at 5 cm, and again at 15 cm H2O PEEP. Volume loading produced a similar increase in cardiac volumes and cardiac index at 5 and 15 cm H2O PEEP. Right and left ventricular performance and left ventricular systolic function were not altered by PEEP (by analyses of covariance). Coronary sinus blood flow and myocardial oxygen consumption increased with volume loading at 5 and 15 cm H2O of PEEP, but myocardial lactate utilization tended to increase at 5 cm, and decrease at 15 cm H2O PEEP (p = 0.08). Of the 33 patients who underwent complete hemodynamic and metabolic measurements, 16 increased cardiac lactate utilization at 15 cm H2O PEEP and 17 decreased cardiac lactate utilization at 15 cm H2O PEEP. PEEP decreased cardiac index, perhaps by reducing left but not right ventricular volumes. Volume loading during PEEP restored cardiac index and revealed no depression in myocardial performance or systolic function. With the application of PEEP, myocardial metabolism was maintained in half the patients, but ischemic metabolism was observed in the other half.

Blood Pressure↗
PubMed1985

Myocardial metabolism and ventricular function following cold potassium cardioplegia.

Transient alterations in myocardial metabolism and ventricular function were observed after elective coronary bypass grafting despite apparently adequate intraoperative protection with cold potassium cardioplegia. Ninety patients had serial hemodynamic measurements and coronary sinus catheters inserted. Thirty-three patients had thermodilution coronary sinus flow catheters inserted to measure coronary sinus blood flow and to evaluate the myocardial utilization of oxygen and lactate. Nuclear ventriculograms were performed in 43 patients to assess ventricular function. Cardiac index fell after discontinuation of cardiopulmonary bypass and then rose between 2 and 24 hours postoperatively. Myocardial oxygen consumption steadily increased during this period. Myocardial lactate production reverted to lactate extraction 30 minutes after reperfusion. Reactive hyperemia was present during the first 10 minutes after cross-clamp release, and coronary sinus blood flow increased gradually during the first 24 hours postoperatively. The response to the stress of volume loading (the infusion of 250 to 500 ml of a colloid solution) and atrial pacing (at a rate of 110 beats/min) was evaluated 2 to 4 hours postoperatively (EARLY) and between 4 to 6 hours postoperatively (LATE). Volume loading resulted in a decrease in lactate extraction EARLY and an increase LATE (EARLY: -0.07 +/- 0.35 mmol/L; LATE: 0.08 +/- 0.32 mmol/L, mean +/- standard deviation not significant). Atrial pacing resulted in a decrease in lactate extraction EARLY and an increase LATE (EARLY: -0.11 +/- 0.34 mmol/L; LATE: 0.14 +/- 0.36 mmol/L, p less than 0.05). Diastolic compliance (the relation between the end-diastolic volume index) decreased between EARLY and LATE. Systolic function (the relation between the systolic blood pressure and the end-systolic volume index) and myocardial performance (the relation between the left ventricular stroke work index and the end-diastolic volume index) were unchanged. Ejection fraction correlated inversely with the end-diastolic volume index and did not represent an independent index of contractility. After elective coronary bypass grafting and cold crystalloid cardioplegia, myocardial metabolism recovered slowly. Hemodynamic stresses should be avoided in the early postoperative period to prevent progressive ischemic injury.

Adult↗
PubMed1985

Right ventricular dysfunction following cold potassium cardioplegia.

Right coronary artery stenoses limit cardioplegic delivery to the right ventricle and may contribute to postoperative right ventricular dysfunction. Right ventricular function was evaluated in 39 patients with right coronary artery stenoses following elective coronary bypass operations. Hemodynamic and nuclear ventriculographic measurements, made between 3 and 6 hours postoperatively, revealed a progressive increase in pulmonary arterial pressure, pulse rate, and right ventricular ejection fraction (p less than 0.05). Right ventricular end-diastolic volume index (calculated from the thermodilution stroke index divided by the nuclear ejection fraction) decreased, but right atrial pressure increased (suggesting a decrease in compliance). The response to the infusion of 2 units of plasma (volume loading) was evaluated 3 hours postoperatively (EARLY) and again 5 hours postoperatively (LATE) in 21 patients. Right ventricular performance (the relation between cardiac index or right ventricular stroke work index and right ventricular end-diastolic volume index) and right ventricular systolic function (the relation between systolic pulmonary arterial pressure and right ventricular end-systolic volume index) were depressed EARLY and improved LATE (p less than 0.01 in analysis of covariance). Left ventricular performance (the relation between cardiac index or left ventricular stroke work index and left ventricular end-diastolic volume index) and left ventricular systolic function (the relation between systolic blood pressure and left ventricular end-systolic volume index) were similar EARLY and LATE. Right ventricular diastolic function (the relation between right atrial pressure and right ventricular end-diastolic volume index) and left ventricular diastolic function (the relation between left atrial pressure and left ventricular end-diastolic volume index) were significantly greater LATE than EARLY. Right, but not left, ventricular performance and systolic function were transiently depressed, and right and left ventricular diastolic stiffness were transiently decreased in the EARLY postoperative period. In patients with right coronary artery stenoses, current methods of cardioplegia may inadequately protect the right ventricle, but further studies are required to establish the relation between intraoperative protection and postoperative function.

Blood Pressure↗
PubMed1984

Rewarming hypovolemia after aortocoronary bypass surgery.

Coronary bypass performed with moderate systemic hypothermia (25 degrees C) and cold-potassium cardioplegia was associated with a fall and subsequent rise in core (pulmonary arterial) temperature. Serial hemodynamic measurements during rewarming and recovery revealed a decrease in cardiac index (CI) without a decrease in the left atrial pressure (LAP) of 17 patients recovering from uneventful coronary bypass surgery. Nuclear ventriculograms performed during rewarming demonstrated a decrease in left ventricular end-diastolic volume index (EDVI, calculated from the thermodilution stroke index divided by the nuclear ejection fraction) without a change in LAP. Volume loading during both mild hypothermia (35 +/- 5[SD]degrees C) and normothermia revealed that myocardial performance (the relation between CI and EDVI) was unchanged, but diastolic compliance (the relation between LAP and EDVI) decreased with rewarming. LAP was a poor indicator of left ventricular preload (EDVI) during rewarming, and volume loading was required to maintain preload and prevent hypoperfusion.

Atrial Function↗
PubMed1984

Limitations of blood conservation.

Blood conservation has been most successful when blood salvage techniques have been combined with postoperative normovolemic hemodilution. The hemodynamic and myocardial metabolic responses to normovolemic hemodilution were assessed in a prospective randomized trial. Twenty-seven patients were randomized to receive either blood and colloid solutions (colloid group, 13 patients) or crystalloid fluids (crystalloid group, 14 patients) following elective coronary revascularization. Although seven patients in the crystalloid group received blood products when the hemoglobin level fell below 7 gm/dl, blood bank requirements were less in the crystalloid group (colloid, 3.6 +/- 1.2 L; crystalloid, 1.5 +/- 1.0 L, p less than 0.01). The crystalloid group received twice as much fluid to maintain normovolemia (left atrial pressure between 8 and 10 mm Hg) in the first 72 hours postoperatively (colloid, 6.5 +/- 1.9 L; crystalloid, 14.5 +/- 3.1 L, p less than 0.01). The infusion of large volumes of crystalloid fluids resulted in a progressive postoperative anemia (hemoglobin: colloid, 12.1 +/- 1.6 gm/dl, crystalloid 8.9 +/- 1.7 gm/dl, p less than 0.01, 20 hours postoperatively). Although the crystalloid-treated patients had peripheral edema, pulmonary edema could not be documented and there was no difference in the physiological shunt fractions between the two groups. Preload (left atrial pressure), afterload (mean arterial pressure), and cardiac index were similar in the two groups. The crystalloid group had a delayed recovery of myocardial oxygen and lactate extraction postoperatively. Volume loading and atrial pacing 3 to 5 hours postoperatively maintained myocardial lactate extraction in the colloid group but decreased myocardial lactate extraction to ischemic levels in the crystalloid group. The use of crystalloid rather than colloid fluids in the early postoperative period conserved blood products but resulted in postoperative anemia and was associated with a delay in myocardial metabolic recovery. Normovolemic hemodilution should be employed with caution in patients who are at risk of perioperative ischemic injury.

Blood Transfusion↗
PubMed1984

A clinical trial of blood and crystalloid cardioplegia.

Although experimental studies suggest that blood cardioplegia provides better protection than crystalloid cardioplegia, clinical studies have been inconclusive. Ninety patients undergoing coronary bypass grafting were randomized to receive either blood (n = 43) or crystalloid cardioplegia (n = 47). The incidence of perioperative myocardial infarction was lower with blood cardioplegia (blood, n = 0; crystalloid, n = 5; p = 0.06), and the maximum MB isoenzyme of creatine kinase was significantly less with blood cardioplegia (blood, 26.3 +/- 12.6 U/L; crystalloid, 35.6 +/- 17.0 U/L, mean +/- standard deviation; p less than 0.02.) Sixty patients (blood cardioplegia, n = 28; crystalloid cardioplegia, n = 32) had more sensitive measurements to assess the metabolic response to aortic occlusion and to compare the metabolic and functional recovery from the operation. Coronary sinus blood flow (by the continuous thermodilution technique) was significantly lower after cross-clamp removal with blood cardioplegia (blood, 160 +/- 100 ml/min; crystalloid, 220 +/- 120 ml/min; p less than 0.05), indicating less reactive hyperemia. The cardiac production of lactate was significantly less with blood cardioplegia during aortic occlusion (blood, -0.5 +/- 0.9 mmol/L; crystalloid, -0.9 +/- 0.9 mmol/L; p less than 0.05) and immediately after aortic declamping (blood, -0.2 +/- 0.4 mmol/L; crystalloid, -0.7 +/- 0.7 mmol/L; p less than 0.01). Thermodilution cardiac output measurements permitted calculation of the left ventricular stroke work index, and nuclear ventriculograms permitted calculation of the left ventricular end-diastolic volume index and end-systolic volume index. Myocardial performance, systolic elastance, and diastolic compliance were determined from volume loading studies (250 to 500 ml colloid) performed 2 to 4 hours postoperatively. Myocardial performance (the left ventricular stroke work index-left ventricular end-diastolic volume index relation) and systolic elastance (the systolic blood pressure-left ventricular end-systolic volume index relation) were significantly better with blood cardioplegia (p less than 0.01 by multivariate analysis); diastolic compliance (the left atrial pressure-left ventricular end-diastolic volume index relation) was similar. Blood cardioplegia reduced ischemic injury, decreased anaerobic metabolism during arrest, and permitted better functional recovery. Blood cardioplegia provides superior protection for elective coronary bypass grafting and may improve the clinical results in patients with unstable angina and in other high-risk patients.

Anti-Arrhythmia Agents↗
PubMed1984

Improved myocardial protection with blood and crystalloid cardioplegia.

Although the results of coronary artery bypass surgery have been excellent, recent studies have demonstrated transient alterations in myocardial function and metabolism in spite of apparently adequate cardioplegic protection. Blood cardioplegia may provide better protection than crystalloid cardioplegia, but clinical studies remain inconclusive. Critical coronary stenoses limit cardioplegic delivery, and myocardial protection would be improved with either blood or crystalloid cardioplegia if the solution could be delivered beyond the coronary stenosis. The construction of proximal as well as distal anastomoses during a prolonged cross-clamp period permits more uniform cardioplegic delivery and immediate reperfusion when the cross clamp is released. This technique was used in a prospective randomized trial comparing blood and crystalloid cardioplegia. The long cross-clamp technique eliminated temperature gradients induced when cardioplegia was delivered into the aortic root. The technique of cardioplegic delivery may be as important as the solution used for cardioplegic protection.

Blood↗
PubMed1983

A comparison of volume loading and atrial pacing following aortocoronary bypass.

Although cold potassium cardioplegia provides adequate myocardial protection, transient hemodynamic and metabolic instability occasionally occurs after uncomplicated coronary bypass surgery. Two methods to increase cardiac output were compared 2 to 6 hours postoperatively in 24 patients recovering from elective coronary bypass operation. Volume loading increased cardiac index (CI) from 2.1 +/- 0.5 to 2.7 +/- 0.6 L/min/m2 by increasing left atrial pressure (LAP) from 8.6 +/- 3.6 to 13.0 +/- 4.1 mm Hg. Atrial pacing at a rate of 112 +/- 8 beats per minute increased CI from 2.4 +/- 0.5 to 2.7 +/- 0.8 L/min/m2 without a change in LAP. Ejection fraction by nuclear angiography did not change, but the calculated left ventricular end-diastolic volume index (stroke index/ejection fraction) increased with volume loading and decreased with atrial pacing--a decrease in diastolic compliance. Myocardial oxygen extraction did not change, but myocardial lactate extraction increased with volume loading and decreased with atrial pacing. Coronary sinus blood flow was measured in 5 patients and increased with both methods studied. Volume loading demonstrated that myocardial performance was normal and myocardial metabolism increased commensurate with the increase in work. Atrial pacing increased CI but resulted in anaerobic metabolism and a decrease in diastolic compliance. Volume loading rather than atrial pacing will improve CI without producing ischemia in the early postoperative period.

Adult↗
PubMed1983

Improved myocardial protection during a prolonged cross-clamp period.

Severe coronary stenoses limit delivery of cardioplegic solution to ischemic regions in patients undergoing bypass operations. A prospective randomized trial was undertaken to determine whether the construction of proximal as well as distal anastomoses during a prolonged cross-clamp period would provide more uniform cardiac cooling and better myocardial protection. Ninety-one consecutive patients undergoing elective coronary bypass operations were randomized into two groups. The long cross-clamp technique was used in 46 patients (Group 1), and a proximal anastomosis was constructed after each distal anastomosis. The short cross-clamp technique was employed in 45 patients (Group 2), and distal anastomoses were constructed during aortic occlusion. Cardiopulmonary bypass time was identical, but the cross-clamp period was longer in Group 1 (59 +/- 15 minutes versus 46 +/- 17 minutes in Group 2; p less than 0.001). The mean temperature in the most ischemic region was colder with the long cross-clamp technique (12.5 +/- 3.1 degrees C in Group 1 versus 14.8 +/- 3.2 degrees C in Group 2; p less than 0.01). The total amount of the myocardial isoenzyme of serum creatine kinase released was greater in Group 2 than in Group 1 (332 +/- 34 IU/L per hour in Group 1 versus 469 +/- 45 IU/L per hour in Group 2). Thirty-six patients had coronary sinus catheters inserted (18 patients in each group). Myocardial lactate extraction returned to normal sooner in the patients who had a long cross-clamp period; time to a normal lactate extraction was 0.8 +/- 0.8 hours in Group 1 versus 2.2 +/- 2.1 hours in Group 2 (p less than 0.001). Volume loading and atrial pacing 2 to 4 hours postoperatively produced a similar hemodynamic response in the two groups, but myocardial lactate extraction increased in Group 1 and decreased in Group 2 (p less than 0.05). The construction of proximal as well as distal anastomoses during a prolonged cross-clamp period produced more uniform cooling and improved myocardial protection.

Constriction↗
PubMed1983

Optimal postoperative volume loading.

Intravenous infusions are required to maintain ventricular preload after uneventful coronary bypass operation. During the early postoperative period, when myocardial metabolic recovery is incomplete, volume loading is intended to stabilize ventricular function and metabolism and to prevent progressive ischemic injury. This study attempts to define the optimal preload for both metabolism and performance. Thirty-seven patients recovering from elective coronary bypass operations and cold potassium cardioplegia underwent volume loading with whole plasma. The initial response (VLA) from a low left atrial pressure (LAP = 7.3 +/- 3.3 mm Hg) was compared with the subsequent response (VLB) from a higher filling pressure (LAP = 10.9 +/- 2.7 mm Hg). Both VLA and VLB produced a similar increase in cardiac index, stroke work index, and end-diastolic volume index (EDVI), and a decrease in ejection fraction (measured by nuclear angiography). Myocardial lactate extraction increased with VLA, but myocardial lactate production resulted with VLB. A careful analysis of these volume loading studies suggested that myocardial performance and compliance were not altered in the early postoperative period. The decrease in ejection fraction with volume loading may have resulted from a combination of increased wall tension and decreased inotropic stimulation. After uneventful coronary bypass surgery, an LAP between 5 and 12 mm Hg corresponded to an EDVI between 30 and 80 ml/m2 and produced adequate cardiac index, stroke work index, and lactate extraction. A lower or higher preload did not improve function and resulted in abnormal metabolism.

Coronary Artery Bypass↗
PubMed1983

Effects of postoperative hypertension and its treatment.

Hypertension following aorta-coronary bypass operations can contribute to myocardial ischemia. Nitroprusside therapy will reduce afterload, preload, and coronary perfusion pressure. Since both hypertension and its treatment can result in ischemic injury, nitroprusside must be carefully titrated to optimize cardiac function and metabolism. Thirty-one patients undergoing elective coronary bypass grafting were studied during a hypertensive episode (mean arterial pressure [MAP] = 119 +/- 18 mm Hg) and during nitroprusside therapy at an MAP of 97 +/- 11 mm Hg and at an MAP of 80 +/- 11 mm Hg (normotension). Nitroprusside also produced a significant (p less than 0.05) decrease in left atrial pressure (LAP), left ventricular end-diastolic volume index (EDVI) (stroke index divided by ejection fraction by nuclear angiography), stroke index, and stroke work index (SWI). Cardiac lactate extraction (LEx) and the ratio LEx/SWI increased (p less than 0.05) with the initial nitroprusside therapy, but lactate production resulted when the MAP was lowered to 80 mm Hg. Volume loading studies were performed during hypertension in four patients and during nitroprusside therapy in 15 patients. Neither performance nor compliance was significantly altered at an MAP of 97 mm Hg, but compliance decreased at normotension. Both hypertension and its treatment can result in inadequate myocardial metabolism. Nitroprusside should be titrated to maintain MAP between 90 and 100 mm Hg.

Adult↗
PubMed1983

Comparison of alternative cardioplegic techniques.

Cold potassium cardioplegia provides adequate protection for coronary bypass operations, but severe coronary stenoses limit cardioplegic delivery to ischemic regions. The traditional technique delivers cardioplegic solution into the aortic root during the performance of distal anastomoses. The proposed alternative technique constructs proximal as well as distal anastomoses during a prolonged cross-clamp period, but permits more uniform cooling. The two techniques were compared in a prospective concurrent trial of 45 patients undergoing elective coronary bypass grafting. The traditional technique was employed in 26 patients (Group A) and the alternative technique in 19 patients (Group B). In both groups, 700 to 1,000 ml of a crystalloid cardioplegic solution was infused into the aortic root after application of the aortic cross-clamp. In Group A (traditional technique), 500 ml was infused into the aortic root after each distal anastomosis. In Group B (alternative technique), cardioplegic solution was administered through the vein graft after each distal anastomosis, and a proximal anastomosis was constructed after distal anastomoses to the most ischemic regions to permit continued cardioplegic delivery to these regions. The cross-clamp period was shorter in Group A than in Group B (44 +/- 15 versus 60 +/- 18 minutes, p less than 0.01), but the mean temperature in the most ischemic region was warmer (Group A, 19 degrees +/- 3 degrees C; Group B, 15 degrees +/- 3 degrees C, p less than 0.05). The postoperative CK-MB was higher in Group A (Group A, 47 +/- 36; Group B, 21 +/- 9 IU/L, p less than 0.01). Cardiac lactate production persisted longer in Group A (Group A, 4 +/- 1; Group B, 1 +/- 1 hours postoperatively, p less than 0.05). Volume loading 4 hours postoperatively produced a similar increase in left atrial pressure and cardiac index in both groups. In response to volume loading, Group A patients produced lactate, but Group B patients extracted lactate (change in cardiac lactate extraction: Group A, -1.7 +/- 2.3; Group B, +2.5 +/- 5.1 mg/dl, p less than 0.05). The construction of proximal as well as distal anastomoses during a prolonged cross-clamp period permits more uniform cooling and immediate reperfusion. This alternative technique resulted in less injury (CK-MB release) and more rapid recovery of myocardial metabolism.

Aged↗
PubMed1981

The hemodynamic and metabolic response to pacing after aortocoronary bypass.

Long-term follow-up of aortocoronary bypass has shown good preservation of ventricular function. However, myocardial reserve in the immediate postoperative period may not be optimal. Nineteen patients who underwent elective aortocoronary bypass protected with cold potassium cardioplegia were studied in the early postoperative period at rest and during the stress of atrial and ventricular pacing. Performance was assessed by hemodynamic, metabolic and nuclear angiographic measurements. In the first 2--6 hours after aortic cross clamping, myocardial performance was preserved at rest and there was no evidence of ischemic metabolism. Atrial pacing at a rate of 119 beats/min caused a significant increase in cardiac index (p less than 0.01) without deterioration in hemodynamics, ejection fraction or metabolic status. At the same rate, ventricular pacing did not change the cardiac index and there was a decrease in hemodynamic function. Ejection fraction decreased from 56% to 44% (p less than 0.05) without a change in end-diastolic volume. Lactate, pyruvate and beta hydroxybutyrate extractions were changed to net production. Ventricular performance was preserved at rest immediately after aortocoronary bypass done with multidose cold potassium cardioplegia, with adequate reserve to meet the stress of atrial but not ventricular pacing. We conclude that the therapeutic implications of the type of pacing selected in the immediate postoperative period may be important.

Atrial Function↗