The surgical outcome of patients requiring conversion to cardiopulmonary bypass (CPB) during myocardial revascularization using the less invasive surgical approach (LISA) was assessed. The LISA was recently introduced as a technique for complete myocardial revascularization without CPB. It combines avoidance of CPB with the versatility of a median sternotomy for access to all coronary vessels. We have previously demonstrated reduced risk-adjusted mortality and complications in off-CPB coronary artery bypass grafting (CABG) using LISA compared to standard myocardial revascularization. From January to December 1997, 1210 patients underwent isolated CABG at our institution. Of these patients, 832 (63%) were scheduled as on-CPB cases and 378 (37%) as off-CPB. Of the off-CPB patients, 48 were converted to CPB. Team A surgeons used LISA as their primary strategy for CABG whereas team B surgeons used off-CPB CABG in selected patients. Conversions were divided in three classes: Class I patients were converted when the surgeon considered complete revascularization impossible off-CPB; Class II patients were converted due to hemodynamic instability during the procedure; and Class III patients were converted due to graft malfunction, determined by flow measurements or clinical evidence. There were four deaths. All had perioperative infarctions and required intra-aortic balloon pump (IABP). Conversion to CPB occurred in up to 25% of patients scheduled for off-CPB CABG. When off-CPB cases are done using the comprehensive LISA technique and modern technology, conversion rates may be reduced to 11%. Conversion is in general well tolerated except when it is instituted for graft malfunction combined with hemodynamic instability or collapse.

1 The cardiovascular effects of the pyridazinone-derivatives pimobendan and its O-demethylmetabolite UD-CG 212 Cl (2-(4-hydroxy-phenyl)-5-(5-methyl-3-oxo-4,5-dihydro-2H-6-pyridazinyl) benzimidazole HCI) were studied in conscious pigs, employing consecutive intravenous 10 min infusions of 10, 25, 50 and 100 pg kg-'min-' and 2, 4 and 8 pg kg-'min-' respectively. 2 Pimobendan caused dose-dependent increases in LVdPIdtmaX (up to 115%) and heart rate (up to 30%), while cardiac output was slightly elevated (up to 15%) and stroke volume decreased by 12%.Left ventricular end-diastolic pressure decreased in a dose-related manner from 8.7 ± 1.0 mmHg to 2.7 ± 1.7 mmHg. Mean arterial blood pressure was not significantly affected because systemic vascular resistance decreased dose-dependently up to 15%.3 After P-adrenoceptor blockade, the pimobendan-induced increases in heart rate and cardiac output were attenuated and the increase in LVdP/dtn,,X almost abolished. The responses of left ventricular enddiastolic and mean arterial blood pressure, systemic vascular resistance and stroke volume were not modified.4 UD-CG 212 Cl caused dose-related increases in LVdP/dt,,mx (up to 100%) and heart rate (up to 25%). Cardiac output was minimally elevated (up to 8%) as stroke volume decreased dosedependently up to 15%. As systemic vascular resistance decreased up to 12%, mean arterial blood pressure was slightly reduced (5%). Left ventricular end-diastolic blood pressure decreased dosedependently from 9.0 ± 0.8 mmHg to 3.8 ± 1.3 mmHg.5 After P-adrenoceptor blockade, the UD-CG 212 Cl-induced increases in heart rate and LVdP/dtmax were attenuated and almost abolished and amounted up to 15% and 20%, respectively. The responses of the other systemic haemodynamic parameters were not significantly modified. 6 We conclude that pimobendan and UD-CG 212 Cl are compounds with marked positive inotropic and venodilator properties in the conscious pig. The attenuation of the inotropic effects by pretreatment with propranolol strongly suggests that, in the conscious pig, the P-adrenergic system is significantly involved in the positive inotropic actions. The lack of effect of P-adrenoceptor blockade on the vasodilator responses to both compounds suggest a mechanism not related to fi-adrenergic activity. IntroductionThe pyridazinone-derivative pimobendan (UD-

A 2 7•y ear~l d woman wh o had previou sly undergone subeo rtic septal my ectomy fo r idiopathic hypertroph ic subaort ic stenosis presented in severe co ngestive failure with echocardiogra phic and angiographic features of aortic valve " vegetatio ns". At operat ion, papillary fi broelastomas of t he aort ic and mitral valves were found. Th e controversy surrounding t he et iology o f these "tumo rs" is d iscussed .

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