Effects of AV Sequential Versus Asynchronous AV Pacing on Pulmonary Hemodynamics

Abstract

We studied the effects of various pacing modes on cardiac hemodynamics and pulmonary gas alterations in chronic heart blocked dogs. Changing the pacing mode from an atrioventricular interval of 100 ms (AV100) to a ventriculo-atrial interval of 100 ms (VA100) caused a significant fall in left ventricular pressure (117.64 +/- 11.91 to 95.60 +/- 16.58 mmHg) and cardiac output from 2.18 +/- 0.24 to 1.46 +/- 0.20 L/min. Following the change in pacing mode from AV100 to VA100, there was an increase in the alveolar-arterial O2 gradient from 23.28 +/- 6.97 to 28.74 +/- 8.43 mmHg and a decrease in the arterial CO2 tension from 32.42 +/- 3.22 to 29.42 +/- 3.22 mmHg. There was also a decrease in arterial CO2 tension when the AV100 pacing mode was compared to asynchronous ventricular pacing (32.42 +/- 3.22 versus 30.56 +/- 2.82 mmHg). The minute volume of O2 also decreased when the pacing mode was changed from AV100 to asynchronous ventricular pacing (0.134 +/- 0.01 versus 0.126 +/- 0.01 L/min) and decreased further at VA100 to 0.114 +/- 0.01 L/min. Other significant changes were also observed: the percent of expired CO2 decreased when the pacing mode was changed from AV100 to VA100 (3.68 +/- 0.13 versus 3.37 +/- 0.26%) or to asynchronous ventricular pacing (3.40 +/- 0.31%). The end-expiratory O2 increased and CO2 decreased when the pacing mode was changed from AV100 to VA100. The breath-by-breath correlation of end-expiratory O2 and CO2 with left ventricular systolic pressure showed an almost immediate increase in O2 and reduction in CO2 concentration associated with decreasing systolic pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

"Contribuição ao estudo da estimulação ventricular e do atrio ventricular universal em portadores da miocardiopatia chagásica: avaliação clínica e hemodinâmica em repuso e exercício"

“…Foram também avaliadas: a importância da contribuição atrial ao enchimento ventricular; a existência ou não de refluxo sangüíneo pelas valvas atrioventriculares; o desenvolvimento de batimentos cardíacos recíprocos inefetivos; as arritmias atriais por reentrada do estímulo elétrico do marcapasso; e o consumo de oxigênio pelo miocárdio, em cada uma daquelas condições. (OGAWA et al, 1978;NAITO et al 1983;COSTA et al, 1984;MOREIRA et al, 1985;DREIFUS et al, 1986 SMEDGARD et al, 1987;ALT et al, 1988;FETTER et al, 1988;ZEGELMAN et al, 1988;HEDMAN & NORDLANDER, 1989;LAU et al, 1989. ) A estimulação atrioventricular universal tem como principais vantagens a manutenção do sincronismo atrioventricular e a capacidade de elevar a freqüência ventricular quando o nó sinusal é normal.…”