Biomedical subjects

E Delia

Publications and source records attributed to E Delia.

3 recordsLinked to original sources

PubMed1993

An echocardiographic study of the fluid mechanics of obstruction in hypertrophic cardiomyopathy.

OBJECTIVES: The goal of this study was to investigate the hydrodynamic cause of mitral-septal contact and obstruction in patients with hypertrophic cardiomyopathy. BACKGROUND: Mitral-septal apposition has been shown to be the cause of obstruction in patients with hypertrophic cardiomyopathy. With obstruction, characteristic continuous wave Doppler tracings show an increasing acceleration of flow. (Tracing is concave to the left.) METHODS: We studied 24 consecutive patients who had a Doppler echocardiographic pressure gradient > or = 36 mm Hg. We pursued two lines of inquiry. 1) Before the onset of obstruction, we systematically measured the angle between the direction of left ventricular Doppler color flow and the protruding mitral leaflet in early systole. 2) After the onset of obstruction, we qualitatively analyzed the concave contour of the continuous wave Doppler tracings in our patients and developed a hydrodynamic theory of the obstruction phase to explain the characteristic tracings. We present a mathematic model to support this concept. RESULTS: We measured 129 angles. Just before mitral-septal contact, the protruding mitral leaflet projects at a mean 40 degrees and 45 degrees relative to flow in the apical long-axis and apical five-chamber views, respectively. At mitral-septal contact, the obstructing leaflet projects at a mean 52 degrees and 58 degrees relative to flow in the same respective views. Even very early in systole, at leaflet coaptation, 11 of 23 patients had angles > 15 degrees relative to flow. After mitral-septal apposition, obstruction across a cowl-shaped orifice begins. During this stage, the obstructing leaflet projects at a mean 55 degrees and 63 degrees relative to flow. In 22 patients, the continuous wave Doppler tracing of the left ventricular outflow jet showed an increasing acceleration of flow. CONCLUSIONS: Just before mitral-septal contact, the protruding leaflets project at high angles relative to flow. At these high angles, flow drag, the pushing force of flow, is the dominant hydrodynamic force on the protruding leaflet and appears to be the immediate cause of obstruction. The high angle between flow direction and the protruding leaflet precludes significant Venturi effects. Even earlier in systole, at leaflet coaptation, flow drag is dominant in half of the patients, with angles relative to flow > 15 degrees. After obstruction is triggered, it appears from our data and model that the leaflet is forced against the septum by the pressure difference across the orifice. The increasing acceleration of Doppler flow is explained by a time-dependent amplifying feedback loop in which the rising pressure difference across the orifice leads to a smaller orifice and a higher pressure difference.

Adult↗

PubMed1991

Unsuspected mitral stenosis.

PURPOSE AND PATIENTS AND METHODS: We observed a series of patients in whom the diagnosis of mitral stenosis was first discovered in the echocardiography laboratory. Because of this experience, we examined the records of 152 patients with echocardiographic evidence of rheumatic mitral stenosis to determine the clinical characteristics and course of patients with unsuspected mitral stenosis as well as those factors that may have obscured the diagnosis. RESULTS: Of these 152 patients, 18 had mitral stenosis that was unsuspected clinically until the echocardiogram. These patients were elderly, with a median age of 72 years. They were all referred for echocardiography because of cardiac symptoms. Eight patients were referred for evaluation of congestive heart failure. Five patients were referred for evaluation of aortic valve disease. Three patients were referred because of cerebrovascular accidents and atrial fibrillation. The Doppler-determined mean diastolic mitral gradient ranged from 4 to 15 mm Hg (mean: 7 mm Hg). Mitral stenosis ranged in severity from trivial to very severe. Eight patients had moderate to severe mitral stenosis with estimated mitral valve areas less than or equal to 1.5 cm2. Seven had mild or trivial mitral stenosis with estimated mitral valve areas greater than 1.5 cm2. After further evaluation, two patients underwent mitral valve surgery with improvement of congestive failure. In three patients, warfarin therapy was begun to prevent emboli. Thus, five of 18 patients had a significant immediate change in therapy because of the discovery of mitral stenosis. CONCLUSION: The diagnosis of mitral stenosis may not be suspected in the presence of advanced age, other serious cardiac and medical conditions, or mechanical factors that complicate the physical examination. In these patients, mitral stenosis may be hemodynamically significant and may cause significant symptoms.

Adult↗

PubMed1988

Oral disopyramide therapy for obstructive hypertrophic cardiomyopathy.

Seven patients with obstructive hypertrophic cardiomyopathy (HC) were treated with oral disopyramide. Left ventricular outflow tract gradients were estimated using either Doppler or M-mode echocardiography. Gradients were measured before treatment, after acute and chronic dosing, after washout and after rechallenge. Disopyramide serum levels were measured at the time of echocardiography. With the first dose, mean outflow gradient decreased from 64 to 14 mm Hg (p less than 0.0001). This decrease in gradient was still present after long-term oral treatment 23 days later, with a mean gradient of 13 mm Hg (p less than 0.001). After withdrawal from the drug, gradient returned to the pretreatment value, 79 mm Hg. After rechallenge, the gradient once again declined to 30 mm Hg (p less than 0.001). High disopyramide serum levels correlated with lower outflow tract gradients, r = -0.77 (p less than 0.0001). Even at low therapeutic drug levels, there was a 49% reduction in outflow tract gradient. Four patients were symptomatically improved and have been maintained on disopyramide for greater than 1 year. In symptomatic patients, disopyramide acutely decreases obstruction and also provides sustained pharmacologic control of obstruction. Disopyramide should be considered as a good alternative to treatment with adrenergic blockers, calcium antagonists or surgery.

Aged↗