A 32-year-old man with a history of a stab wound to the right upper thigh one year previously presents to the emergency department with complaints of difficulty breathing while lying flat. Physical examination reveals an S3 gallop, hepatomegaly, warm skin and a continuous bruit over the right upper thigh. Which of the following is most likely responsible for his symptoms?
1.Decreased sympathetic output
2.Increased peripheral resistance
3.Increased venous return
4.Decreased contractility
5.Increased pulmonary resistance
sol:
This patient with signs and symptoms of heart failure and a bruit over the site of a prior penetrating trauma has a chronic arteriovenous shunt. Such a shunt results in increased venous return and is a potential cause of high-output heart failure.
Penetrating trauma may lead to formation of a fistula (a direct connection between the high pressure arterial system and low pressure venous system). Fistula formation has the effect of decreasing peripheral resistance because blood traveling through the arteriovenous shunt does not pass through the capillary bed. This decrease in peripheral resistance leads to compensatory sympathetic stimulation of the heart with an increase in contractility, heart rate, and stroke volume. These changes collectively result in increased venous return to the heart, which may lead to heart failure due to volume overload.
King et al. discuss the diagnosis and evaluation of heart failure. They note that the presence of a displaced cardiac apex, an S3 gallop, and findings of interstitial edema and/or pulmonary congestion on chest X-ray are indicative of systolic heart failure. The gold standard for diagnosis is echocardiography to assess left ventricular ejection fraction.
Sigler et al. present a case series of 5 patients with high-output heart failure secondary to aortocaval fistula formation after penetrating abdominal trauma. 4 gunshot wound patients with infrarenal fistulae survived surgical repair, while the lone stab wound patient in severe CHF with a suprarenal fistula died during surgery.
Illustration A shows a renal arteriogram of an arteriovenous fistula in the right kidney secondary to a gunshot wound. Illustration B shows a schematic diagram of an arteriovenous fistula.