OBJECTIVE: The goal was to examine left ventricular (LV) regional contraction alterations and especially, regional inotropic reserve changes in tachycardia-induced heart failure (HF). METHODS: Eleven dogs were chronically instrumented to measure LV pressure and its first time derivative (LV dP/dt), left atrial and aortic pressures and to measure antero-apical (AS), -basal (BS) and postero-apical (PS) subendocardial segmental contractions by ultrasonic crystals. Dobutamine (5-15 micrograms/kg per min) and left atrial pacing (150-240 beats/min) were performed in the control state (C) and in HF induced by chronic right ventricular pacing (240 beats/min, 3 weeks). RESULTS: In HF, as compared with in C, LV dP/dt max decreased and LV end-diastolic pressure and end-diastolic segmental lengths increased (Ps < 0.005). The percentage of systolic shortening was more depressed in PS (from 21 +/- 1% to 7 +/- 1%, P < 0.001) than in AS and BS (from 24 +/- 1% to 17 +/- 1% and from 20 +/- 2% to 13 +/- 1% respectively, Ps < 0.05). During dobutamine infusion, in HF as compared with C, the increases in LV dP/dt max were smaller (dobutamine 15 micrograms/kg per min: HF: + 36 +/- 6% vs C: + 68 +/- 11%, P < 0.01) and the increases in the systolic shortening of the three segments were also smaller. However, the responses of the three segments were similar in HF and in C. During left atrial pacing, LV dP/dt max increased less in HF than in C and the poststimulation potentiation of LV dP/dt max was impaired in HF. However, the responses of the systolic shortening during regular left atrial pacing and the increase in the percentage of systolic shortening of the first poststimulation beat were similar in all regions. CONCLUSION: In tachycardia-induced HF, although LV regional contraction is heterogeneously altered, the inotropic reserve appears to be similarly modified in all regions.
OBJECTIVE: The goal was to examine left ventricular (LV) regional contraction alterations and especially, regional inotropic reserve changes in tachycardia-induced heart failure (HF). METHODS: Eleven dogs were chronically instrumented to measure LV pressure and its first time derivative (LV dP/dt), left atrial and aortic pressures and to measure antero-apical (AS), -basal (BS) and postero-apical (PS) subendocardial segmental contractions by ultrasonic crystals. Dobutamine (5-15 micrograms/kg per min) and left atrial pacing (150-240 beats/min) were performed in the control state (C) and in HF induced by chronic right ventricular pacing (240 beats/min, 3 weeks). RESULTS: In HF, as compared with in C, LV dP/dt max decreased and LV end-diastolic pressure and end-diastolic segmental lengths increased (Ps < 0.005). The percentage of systolic shortening was more depressed in PS (from 21 +/- 1% to 7 +/- 1%, P < 0.001) than in AS and BS (from 24 +/- 1% to 17 +/- 1% and from 20 +/- 2% to 13 +/- 1% respectively, Ps < 0.05). During dobutamine infusion, in HF as compared with C, the increases in LV dP/dt max were smaller (dobutamine 15 micrograms/kg per min: HF: + 36 +/- 6% vs C: + 68 +/- 11%, P < 0.01) and the increases in the systolic shortening of the three segments were also smaller. However, the responses of the three segments were similar in HF and in C. During left atrial pacing, LV dP/dt max increased less in HF than in C and the poststimulation potentiation of LV dP/dt max was impaired in HF. However, the responses of the systolic shortening during regular left atrial pacing and the increase in the percentage of systolic shortening of the first poststimulation beat were similar in all regions. CONCLUSION: In tachycardia-induced HF, although LV regional contraction is heterogeneously altered, the inotropic reserve appears to be similarly modified in all regions.