| Popis: |
We studied the effects of a dihydropyridine calcium blocker, felodipine, on left ventricular (LV) contractile performance and diastolic filling dynamics in conscious dogs with pacing-induced congestive heart failure (CHF) before and after autonomic blockade. Eleven conscious dogs were instrumented to measure micromanometer LV and left atrial (LA) pressure (P) and to determine LV volume (V) from three dimensions. CHF was induced by 4 to 5 weeks of right ventricular pacing. After CHF, the mean LV end-diastolic (ED) P increased (9.7 +/- 2.9 vs. 27.9 +/- 6.8 mm Hg, P.05), LVEDV and end-systolic (ES) V increased and stroke volume (SV) decreased (15.3 +/- 2.4 vs. 9.6 +/- 3.0 ml, P.05). The time constant of LV relaxation (T) (25.9 +/- 2.9 vs. 37.9 +/- 5.1 msec, P.05) and LVES wall stress (WS) (63.4 +/- 21.0 vs. 74.6 +/- 23.7 g/cm2, P.05) also increased. After CHF, felodipine (25 nmol/kg i.v., plasma concentrations 17.4 +/- 3.2 nmol/L) produced significant decreases in LVESP (119 +/- 12 vs. 96 +/- 11 mm Hg, P.05), arterial elastance, total systolic resistance (TSR) (0.11 +/- 0.04 vs. 0.07 +/- 0.03 mm Hg/ml/min, P.05) and LVESWS (74.6 +/- 23.7 vs. 60.2 +/- 17.3 g/cm2, P.05). Felodipine increased the slopes of the ESP-V relation (5.6 +/- 1.5 vs. 7.8 +/- 0.7 mm Hg/ml, P.05), the dP/dtmax-EDV relation (51.4 +/- 6.1 vs. 85.3 +/- 10.1 mm Hg/ml sec, P.05) and the stroke work-EDV relation (69.8 +/- 7.1 vs. 78.9 +/- 7.1 mm Hg, P.05) and shifted all three relations to the left, indicating enhanced contractile performance.(ABSTRACT TRUNCATED AT 250 WORDS) |
