Download Case 038: Faint and distant heart sounds.

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Case 038:
Faint and distant heart sounds.
Authors:
David C Chung MD, FRCPC
Faint & distant heart sounds: 1/4
Thomas YK Chan MD, PhD, FRCP
Affiliation:
The Chinese University of Hong Kong
A 56 year-old woman was admitted to hospital for right femoral hernia repair. She
has always been in good health ever since childhood and could not remember when
she was in a doctor’s office last. She was not taking any medications, did not smoke
and did not drink alcoholic beverages, and had no history of allergy. She weighed 55
kg and was 165 cm tall. Her vital signs were: blood pressure 128/78 mmHg, pulse
rate 64/min and regular, respiratory rate 12/min. Physical examination revealed that
the heart sounds were faint and distant at the traditional apex area of the heart (5th
intercostal space just medial to the left mid-clavicular line) but were clearly heard at
the base. Auscultation of the lungs revealed normal breath sounds and, in addition,
heart sounds that were clearly audible on the right side of her chest. Her
preoperative ECG appears below:
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1. What are the abnormalities seen on this ECG?
The obvious abnormalities are:
Limb leads
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The P wave is negative in lead I and lead II, iso-electric in lead aVF, and
positive in lead III—indicating an abnormal P wave axis in the direction of
the foot and to the right.
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The QRS complex is negative in lead I but positive in lead aVF, indicating
right axis deviation.
Chest leads
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The tall R wave in V1 decreases progressively towards V6 instead of the
normal progression of increasing R wave amplitude towards V6.
Progress of the Case: An astute intern suspected the patient has dextrocardia
and proved his case by repeating the ECG with the electrodes of the right and left
arm reversed and the chest electrodes positioned in mirror-image positions on
the right chest as shown below.
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The ECG he obtained appears below. It shows normal P wave and QRS axes as
well as normal progression of R waves across the chest leads:
NB: A more common condition leading to abnormalities seen in the limbs leads of
the original ECG is reversal of the arm electrodes. If that is the case, the chest
leads would be unaffected and should show normal R wave progression.
2. What is dextrocardia?
Dextrocardia is a positional abnormality of the heart. Around the 4th week of
gestation, the primordial heart tube normally bends to the right, placing the fully
developed heart in the left chest with the cardiac apex pointing in the leftward
direction. In dextrocardia, the primordial heart tube bends to the left, placing the
fully developed heart in the right chest with the apex pointing in the rightward
direction. With matching developments in the great vessels, the right-sided heart
becomes a mirror image of the normal left-sided heart. The incidence is
estimated to be 1 in 10,000 live births. Many of these patients have similar
transposition of organs in the abdomen with a left-sided liver and right-sided
stomach, a condition called situs inversus. Subjects with dextrocardia and situs
inversus have low incidents of accompanying cardiac defects and function
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normally throughout life, their condition being discovered only by accident when
they have an ECG, chest x-ray, and at surgery or autopsy. On the other hand,
subjects who have isolated dextrocardia without situs inversus are prone to have
serious cardiac anomalies.
Progress of the Case: Chest x-ray confirmed that the patient had dextrocardia. There
was no cardiac defects seen on echocardiography, and abdominal ultrasound
confirmed situs inversus.
Further reading
Marelli AJ. Chapter 65 – Congenital heart disease in adults. In Goldman: Cecil
Textbook of Medicine, 22nd edition. Saunders, 2004.