Initial outcome of percutaneous balloon valvuloplasty in rheumatic tricuspid valve stenosis

Interventions in pediatric cardiac catheterization

Since its inception in 1929, cardiac catheterization has undergone many changes. In the last two decades we have seen an evolution in cardiac catheterization from a diagnostic (anatomic and physiologic) to a therapeutic modality. This article highlights some of the more common and newer interventional procedures now performed.

Late results of combined percutaneous balloon valvuloplasty of mitral and tricuspid valves

Although combined mitral and tricuspid stenosis are rarely seen in patients with rheumatic heart disease, when both exist together, combined percutaneous balloon valvuloplasty can be an alternative to surgical treatment in suitable cases. We present the immediate and late follow up results of 12 patients with rheumatic tricuspid and mitral stenosis treated with combined percutaneous balloon valvuloplasty. Twelve patients (11 female, 91.7%; 1 male, 8.3%) with a mean age of 35.3 +/- 6.4 years were enrolled in the study. The patients were followed up for 38.8 +/- 12.6 months. The mitral valve area increased from 1.2 +/- 0.2 cm2 to 2.3 +/- 0.2 cm2 (P < 0.01) and on follow up the mitral valve area did not differ significantly (2.2 +/- 0.2 cm2; P > 0.05). The tricuspid valve area increased from 1.6 +/- 0.3 cm2 to 3.2 +/- 0.2 cm2 (P < 0.01) and on follow up the tricuspid valve area did not differ significantly (3.1 +/- 0.2 cm2; P > 0.05). Two patients (16.6%) had tricuspid restenosis and tricuspid re-valvuloplasty. One other patient (8.3%) was referred to surgery 14 months after the procedure secondary to severe tricuspid regurgitation. In conclusion, this study demonstrates a sustained benefit on late follow up after combined percutaneous balloon valvuloplasty of mitral and tricuspid valves and confirms the efficacy and safety of the procedure as an alternative to surgery in selected cases of combined mitral and tricuspid stenosis.

Effect of electrical stimulus parameters on the development and propagation of action potentials in short excitable fibres

Intracellular action potentials (IAPs) produced by short fibres in response to their electrical stimulation were analysed. IAPs were calculated on the basis of the Hodgkin-Huxley (1952) model by the method described by Joyner et al. (1978). Principal differences were found in processes of activation of short (semilength L less than 5 lambda) and long fibres under near-threshold stimulation. The shorter the fibre, the lower was the threshold value (Ithr). Dependence of the latency on the stimulus strength (Ist) was substantially non-linear and was affected by the fibre length. Both fibre length and stimulus strength influenced the IAP amplitude, the instantaneous propagation velocity (IPV) and the site of the first origin of the IAP (and, consequently, excitability of the short fibre membrane). With L less than or equal to 2 lambda and Ithr less than or equal to Ist less than or equal to 1.1Ithr, IPV could reach either very high values (so that all the fibre membrane fired practically simultaneously) or even negative values. The latter corresponded to the first origin of the propagated IAP, not at the site of stimulation but at the fibre termination or at a midpoint. The characters of all the above dependencies were unchanged irrespective of the manner of approaching threshold (variation of stimulus duration or its strength). Reasons for differences in processes of activation of short and long fibres are discussed in terms of electrical load and latency. Applications of the results to explain an increased jitter, velocity recovery function and velocity-diameter relationship are also discussed.