Effects of combination of ACE inhibitor and angiotensin receptor blocker on cardiac remodeling, cardiac function, and survival in rat heart failure

[Preclinical and clinical profile of Valsartan, a selective angiotensin II type-1 receptor blocker]

Valsartan (Diovan) is a potent, orally active, specific, and highly selective blocker for the AT1-receptor subtype. The antihypertensive effects of oral treatment with valsartan were preclinically demonstrated in the sodium-depleted marmosets, renal hypertensive rats (2K1C), spontaneous hypertensive rats (SHR) and stroke-prone SHR. Moreover, valsartan had protective effects against hypertensive end-organ damage such as cardiac hypertrophy and renal disease. In an investigation of pharmacokinetics and pharmacodynamics in normotensive male volunteers, valsartan was rapidly absorbed with the maximal plasma concentration occurring 2-3 h after oral administration. The elimination half-life was about 4-6 h, valsartan was poorly metabolized, and most of the drug was excreted via feces. Valsartan produced persistent reductions of blood pressure in patients with mild to moderate essential hypertension and had a good safety profile with a wide therapeutic window between the effective pharmacological doses and the toxic doses. Therefore, valsartan is expected to be a safe and effective antihypertensive agent for the treatment of essential and severe hypertension.

Combination of low-dose valsartan and enalapril improves endothelial dysfunction and coronary reserve in Nomega-nitro-L-arginine methyl ester-treated spontaneously hypertensive rats

Combination of nonhypotensive doses of valsartan and enalapril markedly improved survival (+87%) compared with untreated animals (37%) in spontaneously hypertensive rats (SHRs) with endothelial dysfunction. However, the combination had no effect on kidney function, and proteinuria persisted over the 12 weeks of the study. It was hypothesized that the greater survival was due to improvement in endothelial function or coronary vasculature despite blockade of nitric oxide synthase and high blood pressure. Therefore, endothelial function was evaluated in isolated aortic ring and maximal coronary blood flow was studied in isolated perfused SHR hearts (20-24 weeks) treated with -nitro-l-arginine methyl ester (L-NAME) (50 mg/l) for 4 weeks. The animals received vehicle, valsartan 5 mg/kg/d, enalapril 1 mg/kg/d, valsartan 50 mg/kg/d, or the combination valsartan 5 mg/kg/d with enalapril 1 mg/kg/d in drinking water. Normotensive Wistar-Kyoto (WKY) rats were used as control. Blood pressure was measured by telemetry. Histopathology was performed on heart, kidney (hematoxylin-eosin), and aorta (Masson trichrome). L-NAME elevated blood pressure by 50 mm Hg after vehicle (199 +/- 5 mm Hg). Valsartan 50 mg/kg/d completely abolished this increase (150 +/- 4 mm Hg) whereas the valsartan-enalapril combination synergistically decreased blood pressure (-37 mm Hg at 162 +/- 7 mm Hg) compared with monotherapy (valsartan 5 mg/kg/d -10 mm Hg; enalapril 1 mg/kg/d -15 mm Hg). All treatments improved the histopathology, most markedly in those receiving the valsartan-enalapril combination. The severity mean grades for lesions were 2.1, 1.9, 1.7, 1.1, and 0.9 in vehicle-treated SHRs, enalapril 1 mg/kg/d, valsartan 5 mg/kg/d, valsartan 5 or 50 mg/kg/d, and the valsartan-enalapril combination, respectively, compared with 0.02 in WKY rats. Acetylcholine-induced relaxation was significantly greater in treated SHRs than after vehicle (-40% at 0.1 mmol acetylcholine) but the combination induced the maximal relaxation (-85%). The ratio of maximal tension induced by serotonin in rings with and without endothelium was 1.4 and 1.3 in vehicle and valsartan 5 mg/kg/d-treated rats whereas it did not differ from 1 in WKY rats and all other treated groups. The cardiac hypertrophy (+27%) was prevented by valsartan 50 mg/kg/d and the valsartan-enalapril combination. Coronary reserve was significantly increased by valsartan 50 mg/kg/d (+85% at 7.8 +/- 0.7 ml/min/g) and the valsartan-enalapril combination (+42% at 6.0 +/- 0.4 ml/min/g) compared with 4.2 +/- 0.5 (vehicle). This was not different of 8.8 +/- 0.5 (WKYs). Despite the maintenance of a high blood pressure, low-dose valsartan-enalapril significantly improved endothelial function and histopathology and increased coronary reserve in SHRs chronically receiving L-NAME.

Long-term combined therapy with an angiotensin type I receptor blocker and an angiotensin converting enzyme inhibitor prolongs survival in dilated cardiomyopathy

The efficacy of ACE inhibitors (ACEIs) in the treatment of chronic heart failures is well documented. However, ACEIs may provide incomplete blockade of the renin-angiotensin system (RAS) because of the alternative pathways for angiotensin II (All) production. We hypothesized that more complete blockade of RAS by adding an AT1 receptor blocker (ARB) may have greater potential to decrease mortality associated with heart failure and improve cardiac function than monotherapy with ACEIs. The objective of this study was to evaluate the effect of combined therapy on cardiac functions and survival in cardiomyopathic hamsters. Male cardiomyopathic hamsters (BIO TO2) were administered either placebo (group C), enalapril (30 mg/kg/day) (group E), or enalapril (30 mg/kg/day) + valsartan (500 mg/ kg/day) (group EV), starting at the age of 6 weeks. Kaplan-Meier analysis was performed to assess the differences in survival. Cardiac functions were evaluated by echocardiogram and cardiac catheterization. Group EV showed significant increases in fractional shortening, LV dP/dTmax, and deceleration time, and showed significant decreases in left ventricular diastolic dimension, LV dP/dTmin, and early diastolic mitral velocity/atrial systolic velocity. Treatment with enalapril resulted in longer survival compared with placebo. Moreover, life expectancy (median probability of survival: 433 days) increased significantly in group EV compared with group E (P<0.05) as well as group C (P<0.001). It is concluded that combined therapy improved cardiac function and survival compared to placebo or enalapril monotherapy.

[Addition of an angiotensin II receptor blocker to maximal dose of ACE inhibitors in heart failure]

In heart failure, the benefits of adding angiotensin-receptor blockade to ACE inhibitors have been studied only with submaximal doses of ACE inhibitors. We included 20 patients (LVEF 24 7%, NYHA II-III), with no clinical or therapeutic variations in the previous three months, who were receiving maximal doses of ACE inhibitors. We added losartan 50 mg once a day. At six months, SBP decreased (115 8 vs. 106 9 mmHg; p = 0.001), LVEF increased (24.4 7 vs. 34.1 7%; p < 0.001), ventricular end-diastolic volumes decreased (220 58 vs 190 46 ml; p = 0.007), and SPAP decreased (43 8 vs. 35 7 mmHg; p < 0.001). Seven patients improved one degree on the NYHA scale (p = 0.004), but VO2max did not change (20.8 5.2 vs. 21.8 5.0 ml/kg/min, p = 0.120). Plasma levels of norepinephrine, at rest and maximal exercise, brain natriuretic peptide, and renin were similar. After maximum ACE inhibitor doses, the addition of losartan is safe and associated with an improvement in ventricular function and NYHA functional class, but with no change in neurohormonal status.

Angiotensin II Type 1 receptor antagonists in chronic heart failure

Angiotensin II Type 1 receptor antagonists share most but not all of their pharmacological actions with angiotensin-converting enzyme inhibitors. The latter belong to standard heart failure therapy, with proven benefit in terms of morbidity and mortality. Promising data have been provided for angiotensin II Type 1 receptor antagonists in experimental models of heart failure. In patients with hypertension and those with diabetic nephropathy, favourable results have been observed with regards to blood pressure control, reversibility of structural changes or prevention of progression of disease. The currently available clinical trials in heart failure patients with angiotensin II Type 1 receptor antagonists suggest that they may be equivalent to angiotensin-converting enzyme inhibitors, but superiority has not been proven. There is no doubt about their effectiveness with regards to symptoms; however, their effect on hospitalisation and mortality is not unequivocally demonstrated. Further trials are warranted, particularly to define their role in comparison with and in addition to angiotensin-converting enzyme inhibitors and to further characterise heart failure patient populations who derive benefit from angiotensin II Type 1 receptor blockers above and beyond angiotensin-converting enzyme inhibitors, beta-blockers and spironolactone.

Combination treatment with a calcium channel blocker and an angiotensin blocker in a rat systolic heart failure model with hypertension

The mechanism and treatment of hypertensive systolic heart failure are not well defined. We compared the effect of an angiotensin-converting enzyme inhibitor (cilazapril, 10 mg/kg), an angiotensin receptor blocker (candesartan, 3 mg/kg), a calcium channel blocker (benidipine, 1, 3 or 6 mg/kg), and the same calcium channel blocker combined with renin-angiotensin blockers on systolic heart failure in Dahl salt-sensitive (DS) rats. DS rats were fed an 8% Na diet from 6 weeks of age and then subjected to the above drug treatments. Benidipine (1 mg/kg), cilazapril, and candesartan had compatible hypotensive effects and similar beneficial effects on cardiac hypertrophy, gene expression, and survival rate. The combination of benidipine with cilazapril or candesartan was found to have no additional beneficial effects on the above parameters, with the exception of a reduction in atrial natriuretic polypeptide gene expression. On the other hand, candesartan normalized serum creatinine, but serum creatinine was unaffected by either benidipine at 1 or 3 mg/kg or cilazapril. Further, the combined use of benidipine and either candesartan or cilazapril resulted in an additional reduction of urinary albumin excretion in DS rats. Thus systolic heart failure in DS rats is mainly mediated by hypertension, while renal dysfunction of DS rats is due to both hypertension and the AT1 receptor itself. These findings suggest that the combination of a calcium channel blocker with an AT1 receptor blocker or ACE inhibitor may be more effective in treating the renal dysfunction associated with systolic heart failure than monotherapy with either agent alone. However, further studies will be needed before reaching any definitive conclusion on the efficacy of this combination therapy in patients with heart failure.

Myocardial blood flow measurements in rats with simple pulsing contrast echocardiography

Relationship between contrast intensity and ultrasound (US) pulsing interval has been utilized to quantify myocardial blood flow (MBF) during myocardial contrast echocardiography (MCE). We tested if an MCE method employing a simple pulsing sequence during intravenous contrast infusion has the ability to quantify MBF in rats. We performed MCE in 17 rats using a 5- to 12-MHz broadband transducer during microbubble infusion via the femoral vein. Acoustic density (AD) from the anterior wall of the left ventricle imaged in the short axis plane was plotted against the frame number after shortening the pulsing interval (PI) from 1:20 to 1:1 end-systolic ECG gating. The relation between AD and frame number was fitted to a decay function. The rate of the AD decay was decreased during dipyridamole infusion, but was increased by causing coronary stenosis. The AD during long PI imaging remained unchanged during the interventions. Estimated MBF by MCE after correction by heart rate exhibited a close correlation (r = 0.83) with the present "gold standard" of colored microsphere-derived MBF. Thus, the decay rate of the contrast intensity obtained with the high-frequency transducer after abrupt shortening of PI during intravenous microbubble infusion may provide for noninvasive measurement of MBF in rats.

Beneficial effects of angiotensin-converting enzyme inhibition in adriamycin-induced cardiomyopathy in hamsters

This study was performed to determine whether angiotensin (Ang) II-forming enzymes, angiotensin converting enzyme (ACE) and chymase might contribute to the development of adriamycin-induced cardiomyopathy in hamsters. Hamsters were administered adriamycin (2.0 mg/kg per day, i.p.) three times weekly for 2 weeks. In the ACE inhibitor-treated group, the hamsters received lisinopril (20 mg/kg per day, p.o.) for 2 weeks after the last injection of adriamycin. The 4-week mortality rates of the vehicle- and ACE inhibitor-treated hamsters were 44% and 12%, respectively. In comparison to the age-matched hamsters used as the control hamsters, a significant decrease in cardiac function and a significant increase in the ratio of the heart weight to the body weight were observed in the vehicle hamsters. Cardiac ACE activity, but not the chymase activity, in the vehicle hamsters was significantly increased in comparison to that in the control hamsters. In the ACE inhibitor-treated group, the increased ACE activity was reduced significantly, and the cardiac hypertrophy and dysfunction were improved significantly. In adriamycin-induced cardiomyopathic hamsters, cardiac ACE activity was increased and ACE inhibition significantly improved cardiac function and survival rate, indicating that cardiac ACE, but not the chymase, plays the pivotal role in the development of the adriamycin-induced cardiomyopathy.