The Venous

1. Where is the venous hum best heard?

ANS: Just above the clavicle, either medial to the sternocleidomastoid muscle or between its insertions. A venous hum is more likely to be heard on the right side because the right jugular is larger than the left, since it must carry about two-thirds of the intracranial venous drainage.

2. What does a venous hum sound like?

ANS: Sometimes like a continuous roar; at other times like "the sound of the sea" heard by putting a seashell to the ear; and sometimes as a whining sound. The diastolic component is often higher-pitched and louder than the systolic. Probably the only quality that is never present is that of an actual hum!

3. What causes the venous hum?

ANS: Two theories have been proposed.

a. Turbulence caused by a confluence of flow through the internal jugular and subclavian veins as they pour into the superior vena cave.

b. Anterior angulation of the internal jugular vein by the transverse process of the atlas [12]. (This angulation and also the murmur can be shown to increase by turning the head away from the side of the hum.)

4. How can you elicit a venous hum if you cannot hear it by merely placing the stethoscope on the neck?

ANS: a. Ask the patient to sit up with his or her feet on the bed to bring maximum blood volume to the heart from both the lower body and head.

b. Apply the small bell lightly to the right side of the neck, as closely as possible to the clavicle and anterior border of the sternocleido-mastoid muscle or between its insertions. Too much pressure will eliminate the hum.

c. Turn the patient's head away maximally and raise the chin as high as possible.

Note: The hum is often augmented by deep inspiration.

d. When a continuous roar or whine is heard, test for the presence of a hum by applying moderate pressure with the fingers a few inches above the stethoscope. A venous hum will disappear with moderate pressure on the internal jugular vein.

A small bell is invaluable in enabling you to apply airtight light pressure anterior to the sternomastoid muscle.

5. What is the significance of a venous hum that can be elicited without head-turning?

ANS: It suggests that the circulation time is at least normal and may even be faster than normal. The unelicited venous hum is of most help in confirming the presence of hyperthyroidism in the young and in suggesting the diagnosis of apathetic hyperthyroidism in the elderly, i.e., hyperthyroidism with no apparent symptoms or signs of thyrotoxico-sis and often with atrial fibrillation. The nonelicited venous hum is also common in patients with severe uremia with a low hematocrit as well as in pregnant women.

Note: Although a venous hum should always be expected if you are diagnosing hyperthyroidism, the hum may disappear if the patient goes into enough heart failure to slow venous flow.

6. What are the methods of eliminating the venous hum besides applying pressure above or with the stethoscope?

ANS: a. Turn the patient's head toward the side of the hum.

b. Decrease venous return from the jugular veins by placing the patient in a supine position.

Note: Some hyperthyroid patients have a faint, high-frequency, continuous murmur, heard clearly over the thyroid after the venous hum has been eliminated by pressure over the jugular. 7. When does a venous hum mimic (a) PDA or (b) AR?

ANS: a. In some children the venous hum is transmitted downward to the upper chest, and since it sounds like a continuous murmur, it has been mistaken for the murmur of a PDA. b. When only the diastolic component is transmitted downward and it is high-pitched.

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