VALVE-REPLACEMENT IN AORTIC-STENOSIS WITH PREOPERATIVE MEAN GRADIENT LESS-THAN-50MMHG - HEMODYNAMIC OUTCOME

Background and aims of the study: No prior studies have defined pre- v ersus postoperative hemodynamics of large numbers of patients with low mean transvalvular gradients. This was our objective. Methods: Retros pective analysis was undertaken of preoperative and postoperative echo /Doppler data in 294 patients who underwent aortic valve replacement ( AVR) for aortic stenosis (AS). Some 136 patients had a preoperative me an gradient of <50 mmHg. The relationship of preoperative to pre- minu s postoperative (Delta) mean gradient (GRAD), peak valvular velocity ( V-2), left ventricular outflow tract velocity (V-1), V-1/V(2)ratio, V- 2-V-1, and aortic valve area (AVA) were plotted and analyzed such that a 'zero-benefit threshold' from surgery could be estimated. Results: Strong relationships (r >0.80) were noted for GRAD to Delta GRAD, V-2 to Delta V-2, and (V-2-V-1) to Delta(V-2-V-1) with zero-benefit thresh olds of 16 mmHg for GRAD, 2.6 m/s for V-2 and 1.7 m/s for V-2-V-1. The se thresholds were lower in patients who received homografts (II mmHg, 2.2 m/s, and 1.1 m/s respectively), p <0.02. The relationship of pre operative V-1/V-2 to Delta V-1/V-2 and 12 AVA-Delta AVA were weaker (r =0.52 and 0.33 respectively) with zero-benefit thresholds of 0.41 and 2.0 cm(2). Among patients with depressed preoperative cm fractional sh ortening, improvement was confined to those without coexistent coronar y artery disease. Conclusion: This analysis of thresholds of mean grad ient benefit suggests that most patients with low gradient AS improve hemodynamically from AVR. The hemodynamic 'break-even' point averages a mean gradient of 16 mmHg.