Stimulation of the renin-angiotensin system in cats with hypertrophic cardiomyopathy

What Causes Hypertrophic Cardiomyopathy?

Hypertrophic cardiomyopathy (HCM) is a global and relatively common cause of patient morbidity and mortality and is among the first reported monogenic cardiac diseases. For 30 years, the basic etiology of HCM has been attributed largely to variants in individual genes encoding cardiac sarcomere proteins, with the implication that HCM is fundamentally a genetic disease. However, data from clinical and network medicine analyses, as well as contemporary genetic studies show that single gene variants do not fully explain the broad and diverse HCM clinical spectrum. These transformative advances place a new focus on possible novel interactions between acquired disease determinants and genetic context to produce complex HCM phenotypes, also offering a measure of caution against overemphasizing monogenics as the principal cause of this disease. These new perspectives in which HCM is not a uniformly genetic disease but likely explained by multifactorial etiology will also unavoidably impact how HCM is viewed by patients and families in the clinical practicing community going forward, including relevance to genetic counseling and access to healthcare insurance and psychosocial wellness.

Effect of angiotensin receptor blockers and angiotensin-converting enzyme 2 on plasma equilibrium angiotensin peptide concentrations in cats with heart disease

Background

Little is known about the effect of renin angiotensin aldosterone system‐inhibiting (RAASi) drugs on alternative angiotensin peptides (APs) such as angiotensin 1‐7 (Ang1‐7), which are mediated by angiotensin‐converting enzyme 2 (ACE2).

Hypothesis/Objectives

Angiotensin receptor blockers (ARBs) would alter balance of APs and differences would be magnified in vitro by incubation of plasma samples with recombinant human ACE2 (rhACE2).

Animals

Six cats with cardiomyopathy (CM), 8 healthy cats.

Methods

Prospective open label trial. Plasma equilibrium concentrations of APs were measured in healthy cats as well as in CM cats that first received no RAASi drugs (CM_noRAASi) and then after 14 days of PO telmisartan (CM_ARB). Plasma APs also were measured after in vitro incubation with rhACE2.

Results

No significant differences were found between healthy and CM_noRAASi groups. Concentrations of several APs, including angiotensin I (AT1) and angiotensin II (AT2) were significantly different between CM_noRAASi and CM_ARB groups. Incubation with rhACE2 decreased AT1 and AT2 in both groups. The geometric mean concentration of Ang1‐7 was significantly higher in CM_ARB (4.9 pg/mL; 95% confidence interval [CI], 3.7‐6.4 pg/mL) vs CM_noRAASi (3.2 pg/mL; 95% CI, 2.2‐4.7 pg/mL; P = .01) and in CM_ARB + ACE2 (5.0 pg/mL; 95% CI, 3.9‐6.4 pg/mL) vs CM_noRAASi + ACE2 (3.0 pg/mL; 95% CI, 1.7‐5.5 pg/mL; P = .01). The most favorable theoretical AP profile that maximized Ang1‐7 and other alternative APs was CM_ARB + ACE2.

Conclusions and Clinical Importance

Balance between traditional and alternative APs can be favorably shifted using ARBs and in vitro incubation with rhACE2. These data shed light on new AP‐targeting strategies in cats with CM.

Evaluation of benazepril in cats with heart disease in a prospective, randomized, blinded, placebo-controlled clinical trial

Background

Heart disease is an important cause of morbidity and mortality in cats, but there is limited evidence of the benefit of any medication.

Hypothesis

The angiotensin‐converting enzyme inhibitor benazepril would delay the time to treatment failure in cats with heart disease of various etiologies.

Animals

One hundred fifty‐one client‐owned cats.

Methods

Cats with heart disease, confirmed by echocardiography, with or without clinical signs of congestive heart failure, were recruited between 2002 and 2005 and randomized to benazepril or placebo in a prospective, multicenter, parallel‐group, blinded clinical trial. Benazepril (0.5‐1.0 mg/kg) or placebo was administered PO once daily for up to 2 years. The primary endpoint was treatment failure. Analyses were conducted separately for all‐cause treatment failure (main analysis) and heart disease‐related treatment failure (supportive analysis).

Results

No benefit of benazepril versus placebo was detected for time to all‐cause treatment failure (P = .42) or time to treatment failure related to heart disease (P = .21). Hazard ratios (95% confidence interval [CI]) from multivariate analysis for benazepril compared with placebo were 1.00 (0.57‐1.74) for all‐cause failure, and 0.99 (0.50‐1.94) for forward selection and 0.93 (0.48‐1.81) for bidirectional selection models for heart disease‐related failure. There were no significant differences between groups over time after administration of the test articles in left atrium diameter, left ventricle wall thickness, quality of life scores, adverse events, or plasma biochemistry or hematology variables.

Conclusions and Clinical Relevance

Benazepril was tolerated well in cats with heart disease, but no evidence of benefit was detected.

Pharmacodynamics of alacepril in healthy cats

Objectives The aims of this study were to investigate the pharmacodynamics of alacepril and to determine the appropriate dose for clinical usage in cats. Methods Six experimental cats were used. Each cat received alacepril orally at a single dose of 1 mg/kg, 2 mg/kg and 3 mg/kg. Blood samples were collected before administration and at 2, 4, 6, 8, 12, 24, 36, 48 and 72 h after administration to measure serum angiotensin converting enzyme (ACE) activity. Systolic blood pressure was also measured at the same time point. Results Dose-dependent inhibition of ACE activity was observed. Doses of 2 mg/kg and 3 mg/kg alacepril were considered to effectively inhibit ACE activity. There were no significant differences in systolic blood pressue among groups at any time point. Conclusions and relevance Alacepril 2-3 mg/kg q24h may be an appropriate dosage for clinical use in cats.

Azotemia in cats with feline hypertrophic cardiomyopathy: prevalence and relationships with echocardiographic variables

OBJECTIVES

The prevalence of renal azotemia in cats with acquired heart disease is not well documented. The aims of this study were therefore (1) to determine the prevalence of azotemia within a hospital population of cats with hypertrophic cardiomyopathy (HCM), and (2) to evaluate the relationship between echocardiographic variables and plasma urea and creatinine.

ANIMALS, MATERIALS AND METHODS

134 client-owned cats were retrospectively studied including 102 cats with HCM and 32 control cats. A complete physical examination, electrocardiography, systolic arterial blood pressure measurement, thoracic radiographs, and echocardiography were performed. Plasma creatinine and urea were determined in all cats. The animal was considered azotemic if plasma creatinine was >1.8 mg/dL and/or urea >65 mg/dL (i.e. BUN> 30 mg/dL).

RESULTS

The prevalence of azotemia was lower in control cats (25.0%) than in cats with HCM (58.8%) (P=0.003). No significant differences in plasma urea and creatinine were observed between the HCM and control cats. There was no effect of plasma creatinine and urea on conventional echocardiographic variables in cats with HCM.

CONCLUSIONS

Azotemia is a frequent finding in cats with HCM but is not dependent on echocardiographic variables.