Dopexamine unloads the impaired right ventricle better than iloprost, a prostacyclin analog, after coronary artery surgery.

OBJECTIVE: To evaluate the ventricle-unloading properties of dopexamine and iloprost and to compare their effects on right ventricular (RV) function and oxygen transport in patients with low RV ejection fraction (RVEF) after cardiac surgery. DESIGN: A prospective, randomized, double-blind, cross-over, clinical study. SETTING: University hospital. PARTICIPANTS: Twenty patients with proximal total stenosis of the right coronary artery studied immediately after coronary artery surgery. INTERVENTIONS: Treatment drugs were administered in a random order in doses equipotent with respect to cardiac output response. Infusion rates were increased stepwise to induce a 25% increase in cardiac index. A washout period of 60 minutes was allowed between treatments. MEASUREMENTS AND MAIN RESULTS: Central hemodynamics, RV function assessed by the EF (fast-response thermodilution), end-systolic and end-diastolic volumes, and systemic oxygenation were measured before and after the first drug, after the washout period, and after the second drug. Central filling pressures remained constant during treatments. Both drugs decreased pulmonary vascular resistance index, but iloprost was more effective (p < 0.05). Iloprost decreased mean arterial and pulmonary artery pressure, which were unaffected by dopexamine. Dopexamine increased EF significantly more than iloprost (p < 0.001). End-systolic volume index decreased subsequent to dopexamine only (p < 0.001). Iloprost increased intrapulmonary shunt more than dopexamine (p < 0.001). Changes in oxygen delivery, consumption, and extraction were similar. CONCLUSION: The findings suggest that dopexamine is more effective than iloprost for support and unloading of the postoperatively disturbed RV in terms of RVEF and end-systolic volume. The reduction of pulmonary vascular resistance after administration of iloprost without a decrease in end-systolic volume might not be considered a reduction of RV afterload. Iloprost increases the pulmonary shunt fraction, however, more than dopexamine, indicating a more prominent vasodilator effect.

Right ventricle is protected better by warm continuous than by cold intermittent retrograde blood cardioplegia in patients with obstructed right coronary artery.

Preservation of the right-ventricular (RV) myocardium is a clinical challenge especially in patients with occluded right coronary artery, in whom antegrade cardioplegia cannot reach areas distal to the stenosis. Retrograde administration of cardioplegia has been thought to overcome the problem, but it has been blamed for inadequate distribution to the RV and possibly poorer functional recovery of this ventricle. Adapting the hypothesis that warm blood cardioplegia may offer better distribution and a more effective supply of oxygen to the arrested heart, we compared RV function in a randomised trial in patients with significant right and left coronary artery disease, after either warm continuous (warm group, n = 15) or intermittent cold (cold group, n = 14) retrograde blood cardioplegia. Right-ventricular function was assessed by determining the ejection fraction (fast-response thermodilution) and preload-related RV stroke work in repeated measurements. The RV ejection fraction remained steady in the warm group during the postoperative course, while it declined significantly in the cold group after operation and differed from that in the warm group until the second postoperative day (p < 0.05-0.001). The ratio of RV stroke work to right atrial pressure was greater postoperatively in the warm than in the cold group until 6 hours after cardiopulmonary bypass (p < 0.05-0.01). Creatine kinase cardiac isoenzyme release was greater in the cold group (p < 0.01). The relationship between left-ventricular stroke work and corresponding preload did not differ between the groups. It can be concluded that recovery of RV function after coronary surgery was better in terms of ejection fraction and preload-related stroke work with warm continuous cardioplegia than with intermittent cold cardioplegia, this along with lower cardiac enzyme release suggesting better RV protection.

Atrial natriuretic peptide and N-terminal atrial natriuretic peptide in plasma reflect right ventricular volumes following coronary artery surgery.

BACKGROUND: Atrial natriuretic peptide (ANP) and the more stable N-terminal fragment (N-ANP) of prohormone are peptides, released in equimolar amounts from cardiac myocytes in response to atrial stretch or ventricular overload and myocardial ischaemia. Protection of the right ventricular (RV) myocardium during ischaemia in cardiac surgery is difficult, especially in patients with severe right coronary artery (RCA) disease. This prospective study was designed to ascertain a possible relationship between changes in plasma ANP/N-ANP concentration and RV function in RCA-diseased patients. METHODS: Plasma ANP and N-ANP concentrations and RV function, measured by fast-response thermodilution, were determined serially in 15 patients with total RCA stenosis and in another 15 with no significant RCA disease (controls) before, during and after coronary surgery. RESULTS: The RV ejection fraction was lower and the RV end-systolic volume index higher in the RCA-diseased patients than in the controls (P < 0.05) on the second postoperative day, and both ANP and N-ANP were higher in the RCA patients (P < 0.05) from 6 h after cardiopulmonary bypass till the second postoperative day. At the same time the changes in N-ANP concentrations from the levels before induction of anaesthesia correlated with RV ejection fraction and RV volume indexes, but not with heart rate or parameters indirectly reflecting left-sided loading. Right atrial pressure did not differ between the groups nor did it increase significantly during the study. CONCLUSIONS: The relationships found between N-ANP and RV volume indexes and RV ejection fraction suggest ventricular expression of ANP: ANP release may be stimulated by RV distension, the more so the poorer the RV function.

Myocardial cooling and right ventricular function in patients with right coronary artery disease: antegrade vs. retrograde cardioplegia.

BACKGROUND: Protection of the right ventricular (RV) myocardium during ischaemia in cardiac surgery is difficult, especially in patients with severe right coronary artery (RCA) disease. Retrograde coronary sinus cardioplegia is thought to distribute uniformly, but doubts still remain as to its adequacy in RV preservation. This study evaluated distribution of antegrade vs. exclusively retrograde coronary sinus cold blood cardioplegia by assessing myocardial cooling and compared the effects on RV function. METHODS: Fifty-eight patients scheduled for elective coronary artery surgery-29 patients with significant RCA disease and another 29 with no significant RCA stenosis (controls)-were randomised to receive either antegrade or retrograde cold blood cardioplegia through either aortic root or conventional self-inflating coronary sinus catheter (RCA-ante, RCA-retro, C-ante and C-retro groups). RV function was assessed by fast-response thermodilution. Myocardial temperatures were measured in the anterior and posterior wall of the right and left ventricle. RESULTS: Cooling of the posterior wall of the RV was effective only in the control patients given antegrade cardioplegia (14.7 degrees C), whereas in the other groups the lowest myocardial temperatures there remained above 20 degrees C (P < 0.001). In patients with obstructed RCA both antegrade and retrograde cold cardioplegia led to uneven cooling of the myocardium. After cardiopulmonary bypass the RV ejection fraction (RVEF), RV stroke work index (RVSWI) and cardiac index (CI) were significantly reduced in the RCA-retro group, and RVSWI and CI in the C-retro group, too. Regression analysis showed an inverse relationship between the temperatures of the posterior walls of the ventricles and changes in the RVEF and CI. CONCLUSIONS: Retrograde and antegrade cardioplegia alone were not effective in reducing the temperature of the posterior wall of the RV in the patients with obstructed RCA, in whom with retrograde cardioplegia RV haemodynamics were impaired for 1 hour following bypass. Neither retrograde nor antegrade cardioplegia alone can be relied on to protect the posterior wall of the RV in the patients with obstructed RCA.

Combined antegrade-retrograde blood cardioplegia does not protect right ventricle better than either technique alone in patients with occluded right coronary artery.

To study the hypothesis that combined antegrade-retrograde delivery of cardioplegia might overcome the limitations in myocardial protection of either technique alone, we compared the distribution of the different cardioplegic approaches by assessing myocardial cooling and evaluated the effects on right ventricular (RV) function in elective coronary artery bypass grafting (CABG) patients with occluded right coronary artery (RCA). In a randomized trial, 15 patients received exclusively antegrade (ante group), 14 patients received exclusively retrograde (retro group) and 15 patients received combined, alternating antegrade-retrograde (combi group) cold blood cardioplegia. Myocardial temperatures were measured at four sites in the heart. Right ventricular function was assessed by determining the ejection fraction (fast-response thermodilution) and preload-related RV stroke work in repeated measurements. Myocardial cooling was similarly uneven and the posterior wall of the RV remained above 20 degrees C after all three methods of delivering hypothermic (5-7 degrees C) cardioplegia. The RV ejection fraction and preload-related (right atrial pressure) RV stroke work decreased postoperatively similarly in all groups. The results suggest that combined antegrade-retrograde cold blood cardioplegia could not provide more homogeneous myocardial cooling or better RV recovery than either technique alone in three-vessel-diseased CABG patients with occluded RCA.

Conduction disturbances after different blood cardioplegia modes in coronary artery bypass grafting. Including comparison with an earlier patient series.

One-hundred and nine patients undergoing coronary artery bypass grafting were randomized to seven groups according to cardioplegia technique (5 types) and right coronary patho-anatomy (2 types). There were no major intergroup differences in postoperative outcome. Conduction disturbances developed in 26 patients, also without intergroup difference. Factors predictive of conduction disturbances were studied by univariate and multivariate analyses. Patients with such disturbances had lower myocardial temperatures than the others and more often postoperative atrial fibrillation (10/26 vs 15/83, p < 0.05). Comparison of this case series with a prospective study from our hospital in 1988-1989 showed that myocardial protection was superior in the present study. The incidence of right bundle branch block was similar in the two studies (24% vs 23%), but that of left-side conduction disturbances (bundle branch or fascicular block) was dramatically reduced (19% vs 1%, p < 0.0001) concomitantly with improved myocardial protection, indicating that development of a left-side conduction disturbance is associated with myocardial injury.

Atrial fibrillation after blood and crystalloid cardioplegia in CABG patients.

In an investigation of factors influencing the occurrence of supraventricular arrhythmias, ninety-eight patients were randomized to receive either cold blood (n = 49) or cold crystalloid (n = 49) cardioplegia during an elective coronary artery bypass grafting operation and were followed for seven days for the development of postoperative atrial fibrillation (AF). Twenty-one patients in the blood-cardioplegia group and nine in the crystalloid-cardioplegia group developed AF (p < 0.01). The patients who developed AF had smaller CK-MB enzyme leaks one hour after the operation (57 +/- 26 iu/L for AF vs 70 +/- 30 iu/L for normal rhythm, p < 0.05), and more often spontaneous beating after cross-clamp release (37% vs 15%, p < 0.05), which indicates that AF was not associated with poor ventricular myocardial protection or conduction system protection. The lesser amount of cardioprotective solution with AF patients (3551 +/- 1585 ml vs 4064 +/- 1562 ml, p < 0.05) and the time of onset of atrial fibrillation (4.0 +/- 1.8 postop. days) indicate that AF is probably caused at least partly by a reperfusion injury at the atrial level. The possibility of atrial fibrillation can be reduced by giving sufficient cardioplegia and giving beta-blocking medicine after the operation.

Rhythm disturbances after blood and crystalloid cardioplegia in coronary artery bypass grafting.

One hundred consecutive patients scheduled for coronary artery bypass grafting were randomized to receive either blood or crystalloid cardioplegia. Successful Holter monitoring for rhythm disturbances was done before and immediately after the operation in 83 cases. With both modes of cardioplegia there were increases in the occurrence of rhythm disturbances postoperatively. The increases were mostly statistically significant. There was no intergroup differences in the occurrence of arrhythmias. The association between these disturbances and cross-clamp times, myocardial temperatures during cross-clamping, myocardial fibrillation times during and after cross-clamping, CK-MB values and perioperative infarction all indicated ischaemia or incomplete myocardial protection as a major cause of the immediate postoperative rhythm disturbances.

Blood and crystalloid cardioplegia in aortic valve surgery.

Eighty-six patients who had undergone aortic valve surgery were reviewed. Forty-three had received crystalloid cardioplegia, the other 43 blood cardioplegia. Spontaneous beating after cross-clamp release (blood 11; crystalloid 0; P < 0.001), number of defibrillations (blood 2.1 +/- 2.6; crystalloid 3.8 +/- 2.2; P < 0.01) and CK-MB values on the operation day (blood 65 +/- 55, crystalloid 112 +/- 73; P < 0.001) and on the following day (blood 53 +/- 43, crystalloid 96 +/- 98; P < 0.01) indicated that blood is a better cardioplegic vehicle for patients with hypertrophied hearts.

Conduction disturbances after blood and crystalloid cardioplegia in coronary bypass surgery.

Postoperative conduction disturbances after coronary artery bypass grafting were analyzed in 100 patients who randomly received either blood or crystalloid cardioplegia. Conduction disturbances, mostly transient, developed after termination of cardiopulmonary bypass in 30 of the 100 patients--15 in either group. Ischaemia appeared to be a major determinant for conduction disturbances. Previous inferior myocardial infarction and stenosis of the right coronary artery both exposed the patient to risk of right bundle branch block.