Infective endocarditis: improved diagnosis and treatment

Recognition and Treatment of Acute Aortic Regurgitation

Acute aortic regurgitation usually results from infective endocarditis, but is also caused by aortic dissection and trauma to the heart. Most of the left ventricular stroke volume is regurgitated back into the left ventricle; thus, the forward stroke volume to the body and the cardiac output may be severely compromised. An acute increase in left ventricular end-diastolic volume results in a marked increase in left ventricular end-diastolic pressure, and the mitral valve usually closes prematurely. Compensatory tachycardia is the rule and helps to shorten diastole; thus, the time available for aortic regurgitation to occur is reduced, and the cardiac output is often maintained.

On physical examination, there is tachycardia; the peripheral arterial pulse shows a rapid rise, but the systolic pressure is normal; the diastolic pressure is normal or even reduced; and the pulse pressure is often normal. The electrocardiogram (ECG) may be normal except for sinus tachycardia and often for nonspecific ST-T changes. The chest roentgenogram usually shows signs of pulmonary venous hypertension or even pulmonary edema. Echocardiography may show vegetations on the aortic valve, prolapse of an aortic leaflet into the left ventricle, and premature mitral valve closure. Doppler echocardiography is useful in detecting the presence of aortic regurgitation.

In cases of infective endocarditis, the appropriate antibiotic therapy must be given. Aortic regurgitation due to dissection of the aorta is usually an indication for surgery. In patients with severe aortic regurgitation, available medical therapy includes digitalis, diuretics, and vasodilators. When patients respond dramatically to the use of digitalis, diuretics, and arterial dilators, surgical therapy can be delayed until heart failure and infection are controlled and the patient is more stable. If the patient does not respond immediately and dramatically to therapy, then valve replacement should not be delayed, even if the infection is uncontrolled or the patient has had little antibiotic therapy.

Hemodynamic effects of nitroglycerin in an experimental model of acute aortic regurgitation

Afterload reduction is an accepted therapeutic modality for the treatment of congestive heart failure caused by chronic aortic regurgitation. However, the role of vasodilator therapy in acute aortic incompetence has not been established. To investigate this, left ventricular volume overload was produced in 18 dogs by constructing a valved conduit from the descending thoracic aorta to the left ventricular apex. The time course of aortic, pulmonary and conduit flows was analyzed in eight control studies and established stability of the experimental model. In the remaining 10 dogs, intravenous nitroglycerin, titrated to reduce mean aortic blood pressure by 40%, and placebo (ethanol) were each infused for 20 min periods. Compared with placebo, nitroglycerin significantly reduced aortic flow (3,945 +/- 324 to 3,397 +/- 362 ml/min, p less than 0.01), regurgitant flow (1,304 +/- 131 to 764 +/- 90 ml/min, p less than 0.001), septal-lateral end-diastolic diameter (47.5 +/- 1.8 to 46.5 +/- 1.8 mm, p less than 0.001), left ventricular end-diastolic pressure (6.9 +/- 0.8 to 6.0 +/- 0.6 mm Hg, p less than 0.05), left ventricular stroke work (19.0 +/- 2.6 to 10.8 +/- 1.7 g-m/beat, p less than 0.001) and systemic vascular resistance (2,253 +/- 173 to 1,433 +/- 117 dyne-s/cm5, p less than 0.001). In contrast, pulmonary flow, left anterior descending coronary flow and subendocardial pH did not change during infusion of either nitroglycerin or placebo. These data indicate that by decreasing preload and afterload, and by preserving coronary flow and tissue pH, nitroglycerin effectively reduced ventricular and regurgitant volumes in the setting of acute volume overload.(ABSTRACT TRUNCATED AT 250 WORDS)

An emergency physician's guide to prosthetic heart valves: valve-related complications

Serious valve-related complications that occur in patients with prosthetic valves have been discussed. The emergency physician's role primarily is to recognize the high probability that one of these serious complications exists and hospitalize the patient so that rapid definitive diagnoses and therapeutic decisions are not delayed.

Patch closure of aortic annulus mycotic aneurysms

Twenty-three patients with bacterial endocarditis and mycotic aneurysms of the aortic annulus were treated between 1978 and 1985. There were 18 men and 5 women ranging from 24 to 72 years old. All patients had congestive heart failure and positive blood cultures as a complication of the endocarditis and were in New York Heart Association (NYHA) Functional Class III or IV. The aneurysm complicated late prosthetic valve endocarditis in 7 patients and native valve endocarditis in 16. The most common infecting organisms were streptococci (12 patients) and staphylococci (7 patients). The noncoronary sinus was the most frequent site for aneurysm formation. Following debridement of the abscess cavity, the orifice of the aneurysm was closed with a patch of Dacron in 20 patients and autologous pericardium in 3. A prosthetic valve (18 bioprosthetic and 5 mechanical) was secured to the noninfected portion of the native annulus and to the patch at the level of annulus. There were 3 deaths, 1 perioperative and 2 late, each without evidence of residual infection or aortic insufficiency. There are 20 late survivors (87%). After a mean follow-up of 1 year, all patients are in NYHA Functional Class I. Patch closure of mycotic aneurysms involving the aortic annulus permits aggressive debridement of the abscess cavity and affords closure of the orifice without tension. The prosthetic valve can be seated at the level of the native annulus, thus avoiding complicated reconstructive procedures of the aortic root and coronary arteries. This technique is an effective alternative in selected cases of mycotic aneurysms involving the aortic annulus.