Influence of heart rate on right ventricular function assessed by right heart catheterization and echocardiography in healthy anesthetized dogs.

BACKGROUND: Right ventricular (RV) functional assessment has received considerable attention in veterinary medicine since various diseases, such as cardiovascular, respiratory, endocrine, and neoplastic disease, may affect RV function. Heart rate (HR) is an important factor that can influence RV function through changes in loading condition and contractility. However, no study has yet evaluated the association between HR and RV function in the same individuals. This study aimed to evaluate the influence of elevated HR on RV function using right heart catheterization and echocardiography, and investigate the association between right heart catheterization and echocardiographic indices. RESULTS: Right atrial pacing was performed in eight dogs at 120, 140, 160, and 180 bpm. With an increase in HR, the RV systolic volume, RV diastolic volume, and stroke volume significantly decreased; however, the cardiac output, end-systolic elastance (Ees), and effective arterial elastance (Ea) significantly increased. Significant changes were not observed in RV pressure and Ees/Ea. The RV area normalized by body weight, RV fractional area change normalized by body weight (RV FACn), and tricuspid annular plane systolic excursion normalized by body weight (TAPSEn) significantly decreased with increased HR. Peak systolic myocardial velocity of the lateral tricuspid annulus (RV s'), RV strain, and RV strain rate of only the RV free wall analysis (RV-SrL3seg) showed no significant changes with the increase in HR; however, there was an increase in the RV strain rate of the RV global analysis (RV-SrL6seg). Multiple regression analysis revealed that HR, RV FACn, and RV- SrL6seg had significant associations with the Ees, and the TAPSEn and RV-SrL3seg with Ees/Ea. CONCLUSIONS: Decreased venous return and shortened relaxation time decreased the RV FAC, TAPSE, RV s', and RV strain, and might underestimate the RV function. Ees increased with the increase in HR, reflecting the myocardial force-frequency relation; as a result, RV-SrL6seg could be a useful tool for Ees estimation. Additionally, the RV-SrL3seg could detect RV performance, reflecting the balance between RV contractility and RV afterload.

Detection of Congestive Heart Failure and Myocardial Dysfunction in Cats With Cardiomyopathy by Using Two-Dimensional Speckle-Tracking Echocardiography.

Congestive heart failure (CHF) is a life-threatening condition in cats with cardiomyopathy. We hypothesized that myocardial dysfunction may induce progression to CHF pathophysiology in cats with cardiomyopathy. However, no previous studies have evaluated the involvement of myocardial dysfunction in cats with CHF. In this study, we aimed to evaluate the relationship between CHF and myocardial function assessed using two-dimensional speckle-tracking echocardiography (2D-STE). Sixteen client-owned healthy cats and 32 cats with cardiomyopathy were enrolled in this study. Cats were classified into three groups: healthy cats, cardiomyopathy without CHF (CM group), and cardiomyopathy with CHF (CHF group). Left ventricular (LV) longitudinal and circumferential strains (SL and SC, respectively), and right ventricular (RV) SL were measured using 2D-STE. Logistic regression analysis was performed to assess the relationship between CHF and echocardiographic variables, including 2D-STE. Results comparing the healthy cats and CM vs. CHF groups showed that increased left atrial to aortic diameter ratio and decreased LV apical SC were significantly associated with the existence of CHF (odds ratio [95% confidence interval]: 1.40 [1.16-1.78] and 1.59 [1.06-2.36], respectively). Results comparing the CM vs. CHF group showed that increased end-diastolic RV internal dimension and decreased RV SL were significantly associated with the existence of CHF (odds ratio: 1.07 [1.00-1.13] and 1.34 [1.07-1.68], respectively). Left atrial enlargement and depressed LV apical myocardial function may be useful tools for predicting the progression to CHF in cats. Furthermore, RV enlargement and dysfunction may lead to the onset of CHF in asymptomatic cats with cardiomyopathy.

Pulmonary Vascular Resistance Estimated by Echocardiography in Dogs With Myxomatous Mitral Valve Disease and Pulmonary Hypertension Probability.

Post-capillary pulmonary hypertension (PH) is a life-threatening complication in dogs with myxomatous mitral valve disease (MMVD). An increase in pulmonary vascular resistance (PVR) is associated with post-capillary PH progression. In humans, PVR estimated by echocardiography (PVRecho) enables the non-invasive assessment of PVR in patients with PH. This study aimed to evaluate the clinical utility of PVRecho in dogs with MMVD, PH probability, and right-sided congestive heart failure (R-CHF). Dogs with MMVD and detectable tricuspid valve regurgitation were included in the study. Dogs were classified into three PH probability groups (low/intermediate/high) and according to the presence or absence of R-CHF. All dogs underwent echocardiographic measurements for right ventricular (RV) morphology and function. PVRecho was calculated by two methods using tricuspid valve regurgitation velocity and velocity-time integral of the pulmonary artery flow (PVRecho and PVRecho2). RV size indicators were significantly higher with a higher probability of PH. RV strain and velocity-time integral of the pulmonary artery flow in the high probability group were significantly lower than those in the other groups. Tricuspid valve regurgitation velocity, PVRecho, and PVRecho2 were significantly higher with an increase in PH probability. Logistic regression analysis revealed a significant association between the presence of R-CHF and increased PVRecho2 and end-diastolic RV internal dimension normalized by body weight. PVRecho and PVRecho2 showed significant differences among the PH probability groups. These non-invasive variables may be useful for the diagnosis and stratification of PH and the determination of the presence of R-CHF in dogs with MMVD.

Right Ventricular Myocardial Adaptation Assessed by Two-Dimensional Speckle Tracking Echocardiography in Canine Models of Chronic Pulmonary Hypertension.

Background: Pulmonary hypertension (PH) is a life-threatening disease in dogs characterized by an increase in pulmonary arterial pressure (PAP) and/or pulmonary vascular resistance. Right ventricle adapts to its pressure overload through various right ventricular (RV) compensative mechanisms: adaptive and maladaptive remodeling. The former is characterized by concentric hypertrophy and increased compensatory myocardial contractility, whereas the latter is distinguished by eccentric hypertrophy associated with impaired myocardial function. Objectives: To evaluate the RV adaptation associated with the increase of PAP using two-dimensional speckle tracking echocardiography. Animals: Seven experimentally induced PH models. Methods: Dogs were anesthetized and then a pulmonary artery catheter was placed via the right jugular vein. Canine models of PH were induced by the repeated injection of microspheres through the catheter and monitored pulmonary artery pressure. Dogs were performed echocardiography and hemodynamic measurements in a conscious state when baseline and systolic PAP (sPAP) rose to 30, 40, 50 mmHg, and chronic phase. The chronic phase was defined that the sPAP was maintained at 50 mmHg or more for 4 weeks without injection of microspheres. Results: Pulmonary artery to aortic diameter ratio, RV area, end-diastolic RV wall thickness, and RV myocardial performance index were significantly increased in the chronic phase compared with that in the baseline. Tricuspid annular plane systolic excursion was significantly decreased in the chronic phase compared with that in the baseline. The RV longitudinal strain was significantly decreased in the sPAP30 phase, increased in the sPAP40 and sPAP50 phases, and decreased in the chronic phase. Conclusions: Changes in two-dimensional speckle tracking echocardiography-derived RV longitudinal strain might reflect the intrinsic RV myocardial contractility during the PH progression, which could not be detected by conventional echocardiographic parameters.

Left and Right Myocardial Functionality Assessed by Two-Dimensional Speckle-Tracking Echocardiography in Cats with Restrictive Cardiomyopathy.

The endomyocardial form of restrictive cardiomyopathy (EMF-RCM), a primary disorder of the myocardium, is one of the diseases with poor prognosis in cats. We hypothesized that both the left and right myocardial functional abnormalities may occur in cats with EMF-RCM, causing this disease pathophysiology and clinical status. Out of the 25 animals included in this study, 10 were client-owned cats with EMF-RCM, and 15 were healthy cats. In this study, cats were assessed for layer-specific myocardial function (whole, endocardial, and epicardial) in the left ventricular longitudinal and circumferential directions, and right ventricular longitudinal direction, via two-dimensional speckle-tracking echocardiography (2D-STE). Cats with EMF-RCM had depressed left ventricular myocardial deformations both in systole (whole longitudinal strain, epicardial longitudinal strain, and endocardial circumferential strain) and diastole (early and late diastolic longitudinal strain rates, and late diastolic circumferential strain rate) compared to controls. Furthermore, some right ventricular myocardial deformations (systolic longitudinal strain in epicardial layers, and endocardial-to-epicardial strain ratio) were significantly differerent in cats with EMF-RCM. Myocardial function assessed by 2D-STE could reveal left and right myocardial dysfunction.