Postoperative exercise tolerance after aortic valve replacement by small-size prosthesis: functional consequence of small-size aortic prosthesis.

OBJECTIVES: The objective of this study was to determine whether a small-size valve prosthesis contributes to exercise intolerance, as assessed by VO2 measurement during an exhaustive cycle ergometer exercise. BACKGROUND: The determinants of exercise capacity after mechanical aortic replacement are not well known. The selection of small valve sizes has, however, been described as an independent predictor of exercise intolerance as assessed by exercise duration. Maximal oxygen uptake (VO2max) is a good index of exercise tolerance. METHODS: Fourteen patients were eligible, with a mean age of 62 +/- 6 years. Before surgery, the mean left ventricular ejection fraction (LVEF) was 73 +/- 8%. Two valve types with small diameter (19 to 21 mm) were used: Medtronic Hall and St Jude Medical. A healthy sedentary control group (n = 14) paired for age, weight and size was constituted. After one year of follow-up, cardiorespiratory tests were performed. In addition, the gradients through the prostheses were determined by continuous pulse Doppler at rest and immediately after the cardiorespiratory test. RESULTS The exercise tolerance was not significantly different between the control group and patient group: VO2 peak (21.7 vs. 20.4 ml/kg/min; p = 0.42), workloads (115 vs. 93 W; p = 0.13) and ventilatory parameters were similar. The mean and peak gradients at rest and during exercise were not correlated with VO2max. CONCLUSIONS: Valve replacement by small aortic prosthesis does not seem to be a factor of exercise intolerance as assessed by VO2max in patients without LVEF dysfunction before surgery.

[Continuous nodal reciprocal rhythm and Steinert's disease: treatment by double chamber stimulation. A case report]. / Rythme réciproque nodal incessant et maladie de Steinert: traitement par stimulation double chambre. A propos d'un cas.

We report a case of continuous supraventricular tachycardia in a patient affected by Steinert's myotonic dystrophy. The investigation of this tachycardia showed that there was a "slow-fast" common nodal re-entry, rendered continuous by the existence of significant conduction defects in the fast pathway and the slow anterograde pathway. Implantation of a double chamber cardiac stimulator, necessary for conduction defects present in the basal state in this patient allowed, with the evolution of the conduction defects, the complete eradication of reciprocal rhythm entry, without resorting to ablation.