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Dynamic right ventricular outflow obstruction: a new cause of systolic murmurs in cats.

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.

Aging↗

Mobilization of the left and right fibrous trigones for relief of severe left ventricular outflow obstruction.

BACKGROUND: There is still no agreement about the optimal method of surgical relief of fixed subaortic stenosis, particularly the severe forms. OBJECTIVES: The purpose of this study was to describe a new technique for the relief of subaortic stenosis based on analysis of the functional anatomy of the left ventricular outflow tract and pathophysiologic features of subaortic stenosis. METHODS AND PATIENTS: We propose that one of the basic abnormalities in subaortic stenosis is interference with the hinge mechanism provided by the 2 fibrous trigones with progressive deposition of fibrous tissue in these angles. The technique described in this paper consists of excision of all components of the fibrous "ring," with mobilization of the left and right fibrous trigones. This results in the restoration of the normal dynamic behavior of the left ventricular outflow tract with maximal widening of the outflow tract as the result of backward displacement of the subaortic curtain and anterior leaflet of the mitral valve. This technique has been used in 57 consecutive patients who ranged in age between 5 months and 56 years (mean, 15.5 +/- 10.6 years). Gradients across the left ventricular outflow tract were between 45 and 200 mm Hg (mean, 86.7 mm Hg). Additional lesions were present in 10 patients, and 7 patients had had 8 previous operations on the left ventricular outflow tract. At operation, in addition to resection of subaortic stenosis, 3 patients had aortic valvotomy, 2 patients had homograft replacement of the aortic valve, 7 patients had patch closure of a ventricular septal defect, and 1 patient had open mitral valvotomy. RESULTS: There were 2 early deaths and 1 late sudden death during the follow-up period that ranged from 1 month to 25 years (mean, 15. 2 years). One patient experienced the development of endocarditis on the aortic valve 7 years after operation, which was successfully treated by homograft replacement. Postoperative gradients across the left ventricular outflow tract varied from no gradient to 30 mm Hg (mean, 8 mm Hg). There were no instances of recurrence of a gradient across the left ventricular outflow tract. CONCLUSION: It is concluded that mobilization of the left and right fibrous trigones results in durable relief of subaortic stenosis.

Adolescent↗