Acute effects of right ventricular pacing in normal hearts.

• Tipo: Resumo de Comunicação em Conferência Internacional
• Data: 2005

Autores

Vasconcelos M (Autor) Outra; Santos M (Autor) FMUP; Brandao-Nogueira A (Autor) Outra; Henriques-Coelho T (Autor) FMUP; Leite-Moreira AF (Autor) FMUP

Ata de Conferência Internacional

Título: European Journal of Heart Failure

Página Inicial: 661

ESC Annual Congress 2005

Stockholm, Sweden , 03 a 07 de Setembro de 2005

Classificação Científica

FOS: Ciências médicas e da saúde > Outras ciências médicas

Outras Informações

Resumo (PT): Background: Asynchronous electromechanical activation of the left ventricle (LV) in patients with left branch block or right ventricular pacing (RVP) leads to asymmetric distribution of load with differences in local blood flow and metabolism. At long-term this process induces asymmetrical hypertrophy and ventricular enlargement leading to heart failure progression. The aim of this study was to investigate the acute effects of RVP on LV haemodynamics. Methods: Male Wistar rats (n=12; 303±20g) were instrumented with pressure tip micromanometers in the LV and pacing wires in the RV free wall. Animals were randomly assigned to two experimental protocols: (i) RV pacing during 2h in order to increase 10% basal heart rate (Pc; n=6); (ii) sham group. In both groups hemodynamic parameters were registered at the beginning and at the end of protocol, with the pacemaker turned-on (Pc) and turned-off. Systolic (SP) and end-diastolic (EDP) pressures, dP/dtmax and dP/dtmin and time constant of isovolumetric relaxation tau were measured. Results presented in table 1 as mean ± SEM (* p<0.05 vs 0 min; + p<0.05 vs Pc0min). Results: Turning on the pace resulted in an impairment of the indices of systolic function (SP and dP/dtmax), which improved progressively during the 2 hours the pace was turned on. This increased myocardial contractility was still observed when the pacemaker was turned-off. Concerning diastolic function we observed increased EDP and a faster relaxation rate (tau decreased) immediately after turning on the pace, an effect that remained during the rest of the experimental protocol. Table 1. Hemodynamic changes induced by right ventricular pacing 0min Pc 0min Pc 120min 120min SP (mmHg) 80.2±6.4 78.9±7.0 92.0±1.3 86.3±9.4 dP/dtmax (mmHg/s) 3478±799 3279±669 4335±966 * + 4455±867 + dP/dtmin (mmHg/s) -2185±466 -2109±412 -2827±622 + -3019±702 + EDP (mmHg) 0.0±7.7 0.8±9.5 1.9±9.9 * + 1.8±9.1 * tau (ms) 29.2±7.7 22.1±2.3 * 21.9±2.4 * 22.1±2.0 * Conclusion: In normal hearts, RVP induced transitory systolic dysfunction, followed by a compensatory response characterized by increased contractility and faster relaxation.

Idioma: Inglês

Tipo (Avaliação Docente): Científica

Notas: 27th Congress of the European-Society-of-Cardiology, published in journal, European Heart Journal. 2005; Vol.26(Abstract.3839)(Suppl1):661-661.