Is This Woman's Heart in the Right Place?

A 53-year-old woman with a history of hypertension presents to the emergency department with excessive vaginal bleeding (requiring 6 or 7 sanitary pads per day), light-headedness, and episodes of near-syncope of 1 month's duration.

Blood pressure is 151/83 mm Hg; heart rate, 70 beats per minute; respiration rate, 20 breaths per minute; temperature, 36.5°C (97.6°F); and oxygen saturation, 99% on room air. The vaginal vault has a copious amount of blood, without tenderness or palpable masses. The abdomen is soft and nontender. Breath sounds are clear and equal. Decreased heart sounds are audible on the left; the sounds are louder on the right.

An ECG reveals a right axis deviation with an anterolateral myocardial infarction of indeterminate age (Figure 1).

A chest radiograph is interpreted as normal; however, it is later noted that the "R" indicator is backward on the film. A second chest radiograph shows that the heart silhouette and gastric bubble are on the right and the elevated hemidiaphragm is on the left (Figure 2). This prompts a working diagnosis of situs inversus.

A sequential series of ECGs is performed, first with the precordial electrodes on the right side of the chest wall and the limb electrodes in the standard locations (Figure 3), then with complete reversal of the limb electrodes and the precordial electrodes on the right side of the chest wall (Figure 4). The transposition of the electrodes normalizes the ECG findings.

EXPLANATION OF ECG FINDINGS

In the initial ECG (Figure 1), the inverted P-QRS-T complex in lead I confirms either a right-sided heart or reversal of the arm electrodes. In cases of arm-electrode reversal, the principal QRS vector in lead I (downward) is opposite that of lead V₆ (upward). In this tracing, the principal QRS vector is negative in both leads I and V₆, which indicates either isolated dextrocardia or, as in this patient, true situs inversus.

Also apparent in the initial ECG is the lack of precordial R-wave progression. In the second ECG (Figure 3), the R waves become progressively larger as the eye moves from V₁ to V₆, and, thus, appear normal; the limb leads are unchanged.

In the final ECG (Figure 4), both the precordial leads and the limb leads appear normal now that the corresponding electrodes have been applied to optimally record the right-sided heart.

SITUS INVERSUS:AN OVERVIEW

Situs inversus is the mirror image of situs solitus--the normal anatomic position. Situs ambiguous, or visceral heterotaxy, refers to the indeterminate or uncertain anatomic layout of certain viscera. In true situs inversus, the right side of the body contains the pulmonary atrium, aorta, bilobed lung, stomach, and spleen, while the left side houses the systemic atrium, inferior vena cava, trilobed lung, liver, and gallbladder. With these transpositions, the pulmonary anatomy also follows suit.¹

Situs inversus occurs in 0.01% of live births, without a racial or sexual predominance. When it is accompanied by bronchiectasis and nasal polyposis with chronic sinusitis, Kartagener syndrome is diagnosed; about 20% of persons with situs inversus have this syndrome. The incidence of congenital heart disease is 3% to 5% in those with situs inversus.^2,3

DIAGNOSIS

Although situs inversus is generally identified with radiography or ultrasonography, CT is the gold standard for distinguishing between dextrocardia and levocardia. This is because of its ability to visualize vessel branching, organ placement, and apical position.⁴

Identification of the condition is crucial to prevent inadvertent morbidity and mortality from incorrect placement of defibrillator pads, missed diagnoses secondary to malposition of viscera, and surgical complications in blunt and penetrating trauma.

PROGNOSIS

Like most patients with situs inversus, this patient lives a normal life without any complications or physiologic disorders. Her presenting symptoms were attributed to dysfunctional uterine bleeding, for which conjugated estrogens were prescribed.

References:

REFERENCES:

1.

Winer-Muram HT. Adult presentation of heterotaxic syndromes and related complexes.

J Thorac Imaging.

1995;10:43-57.

2.

Friedman W, Silverman N. Congenital heart dis-ease in infancy and childhood. In: Braunwald E, Zipes DP, Libby P, Bonow R, eds.

Heart Disease: A Textbook of Cardiovascular Medicine

. 6th ed. Philadelphia: WB Saunders Co; 2001:1505-1591.

3.

Wilhelm A, Holbert JM. Situs inversus. Available at:

http://www.emedicine.com/radio/topic639.htm

. Accessed February 1, 2006.

4.

Applegate KE, Goske MJ, Pierce G, Murphy D. Situs revisited: imaging of the heterotaxy syndrome.

Radiographics.

1999;19:837-852.