Dynamic Right Ventricular Outflow Obstruction: A New Cause of Systolic Murmurs in Cats

Abstract

We have identified and characterized a new cause of variable parasternal systolic murmurs in cats. Color Doppler echocardiography of 51 cats presented for evaluation of a cardiac murmur demonstrated a localized, turbulent systolic jet located within the right ventricular (RV) outflow region, originating just cranial to the tricuspid valve. Spectral Doppler tracings of the turbulent jets showed abnormally high peak velocity, late systolic flow acceleration, and marked variability with heart rate, typical of dynamic stenosis. Frame-by-frame examination of 2-dimensional (2D) echocardiographic images after color Doppler subtraction revealed systolic apposition of the RV free wall with the interventricular septum at the origin of the turbulent jets. Therefore, we termed this turbulent flow pattern "dynamic right ventricular obstruction" (DRVO). Most cats with DRVO were >4 years old (45 of 51, 88%) and initially presented with concurrent noncardiac disease (73%). Noncardiac diseases associated with DRVO in older cats included high cardiac output states (hyperthyroidism, anemia, and inflammatory disease) and chronic renal failure with and without systemic hypertension. Of the 45 cats >4 years old, 4 (9%) had no evidence of any other cardiac or noncardiac disease. In contrast, 5 of 6 cats (83%) <4 years old had concurrent cardiac disease. No breed predisposition was identified. Follow-up examination of 10 cats demonstrated no change in the disorder in 8 cats but revealed the disappearance of the murmur and abnormal RV Doppler flow signal in 2 cats after renal transplantation. We propose that DRVO is a physiologic cause of systolic murmurs in cats attributable to RV systolic narrowing.

Investigation into the use of plasma NT-proBNP concentration to screen for feline hypertrophic cardiomyopathy

“…The sensitivity and specificity of auscultation in detecting cardiac disease in cats is compromised by the absence of auscultatory abnormalities in many cats with HCM, especially those with mild to moderate disease, and the occasional presence of a physiologic murmur, most commonly due to dynamic right ventricular outflow tract obstruction, in cats. 5,6 The sensitivity of thoracic radiography for diagnosing even severe HCM in cats is limited due to the concentric nature of the left ventricular hypertrophy coupled with the more cranial location of the left atrium in cats when compared to dogs. 3 In addition, the specificity of thoracic radiography for HCM is very poor.…”

The Diagnostic Significance of the Plasma N-Terminal Pro-B-Type Natriuretic Peptide Concentration in Asymptomatic Cats with Cardiac Enlargement

“…In contrast, such a drastic symptom was not observed in cats with asymptomatic HCM. Cardiac murmur due to outflow obstruction or systolic anterior motion (SAM) of the mitral valve is not always heard in cats with asymptomatic HCM [4,16,17]. The ability of thoracic radiography to detect ventricular hypertrophy is very low [12,17].…”

Feline hyperthyroidism: diagnosis and treatment

“…Systolic murmurs, grade I-III/VI, the intensity of which varies with heart rate and gallop rhythm, attributed to dynamic left or right ventricular outflow tract obstruction and rapid ventricular filling respectively, are often auscultated (Broussard et al, 1995;Rishniw and Thomas, 2002;Peterson, 2013).…”