In addition to clinical factors, such as advanced age and body surface area, we demonstrated that electrophysiologic changes involving an increase in P-wave dispersion postoperatively independently predict atrial fibrillation after coronary artery bypass graft surgery.

Introduction: Most of the cardiac surgery done today Is performed with aortic cross-clamping and cardlopleglc arrest. Despite Improvements In cardlopleglc techniques, ventricular dysfunction following cardlopleglc arrest Is a major cause of perloperatlve morbidity and mortality. This experiment wJJJ quantify the changes In left ventricular systolic function with cold cardioplegia. Four measures of cardiac function will be assessed with a volume conductance catheter. Methods and Results: Thirty patients undergoing coronary ar· tery bypass graft surgery had volume conductance and mlcromanometer catheters placed In their left ventricles. Preload reduction was used to measure Eaa (the slope of the end-systolic pressure-volume relationship), EdP/dtMax-eov (slope of dP/dtMax end-diastolic volume relationship), EPLRSW (slope of stroke work end-diastolic volume relationship), Eed (slope of the end-diastolic pressure-volume relationship), and ENegdP/dtMax-EDV (slope of the negative dP/dtMax end-diastolic volume relationship). Eaa decreased from 4.32 ± 2.94 prebypass to 2.52 ± 1.06 mmHglmL postbypass. Conclusion: Cold cardlopleglc cardiac arrest Is associated with postbypass systolic and diastolic ventricular dysfunction, which can be quantitated by volume conductance and mlcromanometer based measurements. (J Card Surg 1994;9{Suppl]:497-502) Despite improvements in cardioplegic techniques, post-cross-clamp ventricular systolic and diastolic dysfunction is a major cause of morbidity and mortality associated with cardiac surgery. The exact etiology of this dysfunction is unknown but myocardial ischemia during the period of cardioplegic arrest is a major con-

Atrial fibrillation (AF) is a common complication after coronary artery bypass graft (CABG) surgery. Despite the prevalence of AF occurring after cardiac surgery, its pathophysiology is incompletely understood. Our previous study demonstrated that age and left atrial enlargement were independent predictors of postoperative AF. Accordingly, the purpose of this study was to determine whether cellular changes such as fibrosis and/or hypertrophy occurred in the atrium in patients who subsequently developed postoperative AF. Right atrial appendage tissue was obtained during atriotomy in patients undergoing elective CABG surgery. Quantitative assessment of atrial fibrosis was performed with Sirius red stain, and atrial cell diameter was measured with the HE stain. Linear regression, t test, χ² test or Fisher exact test were used for statistical analysis. Sixty-one patients (mean age 71 ± 8 years) were studied. Increasing age was significantly associated with fibrosis (beta 0.3, 95% CI: 0.06–0.55, p = 0.017). The amount of right atrial fibrosis tended to correlate with the incidence of postoperative AF (p = 0.08). Cell diameter was not significantly different between patients with versus without postoperative AF (p = 0.85). These results suggest that the age-related atrial fibrosis rather than cellular hypertrophy may be important in the pathogenesis of AF after CABG surgery and should be further investigated.

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