ALTERNATING BIDIRECTIONAL TACHYCARDIA

JAIRO VELASQUEZ, M.D.,* AND GEORGE A. KELSER, JR., M.D.**

WASHINGTON, D. C.

B IDIRECTIONAL tachycardia can still be considered an uncommon arrhyth- mia. Since the excellent review of 32 patients by Zimdahl and Kramer’ in

1947, only 3 additional cases have appeared in the medical literature.2t3s4 The mechanism of the production of this arrhythmia remains controversial. However, the poor prognosis associated with the presence of bidirectional tachycardia is uniformly recognized.

The purpose of this report is to show the response of bidirectional tachycardia to the Valsa!va maneuver and oral potassium chloride.

CASE REPORT

%::. R., a 45year-old, unemployed Negro man was admitted to the medical service of the District of Columbia General Hospital on Mar. 16, 19.56, with the chief complaint of severe short- ness of breath of 2 days’ duration.

In 1952, he had been treated at another hospital for a period of 2 months for an acute myo- cardial infarction. Chronic congestive heart failure, manifested by exertional dyspnea and per- sistent lower extremity edema, had required the daily administration of 0.1 Gm. of digitalis leaf and the periodic administration of diuretics since 1952. There was no past history of hypertension.

On admission the physical signs were: Temperature: 37”C., orally; Pulse: ldO/min.; Res- pirations: 40/min.; Blood pressure: 120/80 mm. Hg. He appeared acutely ill and severely dyspneic. Examination of the ocular fundi revealed moderate narrowing and increased tortu- osity of the arterioles. Cervical venous distention was marked. Marked cardiomegaly to the left was evident. The second pulmonic sound was i,ncreased in intensity. A Grade 2 blowing apical systolic murmur was present. Fine and medium inspiratory riles were noted bilaterally. The lower right lung field was dull to percussion and breath sounds were diminished in this area. The liver edge was 12 cm. below the right costal margin in the mid-clavicular line. Moderate ascites and marked pitting edema of the lower extremities were observed.

Laboratory data included the following: hematocrit: 39; hemoglobin: 13 Gm.: white blood count: 8,850, with a differential count of 65 neutrophils and 35 lymphocytes; blood urea nitrogen: 32 mg. per cent; total serum protein: 7.0 Gm. with albumin of 4.0 Gm. and globulin of 3.0 Gm. ; fasting blood sugar: 105 mg. per cent. Chest x-ray demonstrated cardiomegaly with left ventricular preponderance, pulmonary congestion, and a right hydrothorax.

On admission, the electrocardiogram revealed atria1 fibrillation with a rapid ventricular response and an initial 0.04 second deformity of the QRS complex, suggesting the presence of an old diaphragmatic myocardial infarction (Fig. 1).

Hospital Course.-On the day of admission, 0.6 mg. of lanatoside C given intravenously slowed the ventricular response to 106 per minute. He was then given 0.25 mg. of digoxin orally

From the George Washington Medical Division. District of Columbia General Hospital, and the Department of Medicine, the George Washington University Medical School, Washington. D. C.

Received for publication Dec. 14, 1956. *Former Fellow in Cardiology. the George Washington University Medical Division, District of

Columbia General Hospital, Washington. D. C. **Instructor in Medicine, the George Washington University Medical School, Washington. D. C.

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iYiE “j’ ALTERNATING BIDIRECTIONAL TACHYCARDIA 441

twice daily. Forty-eight hours after admission, and after receiving a total of 1.0 mg. of digoxin by mouth, a repeat electrocardiogram revealed alternating bidirectional tachycardia (Fig. 2). Carotid sinus pressure did not alter the arrhythmia. However, the Valsalva maneuver produced the effect illustrated in Fig. 2. Digitalis was discontinued. Oral potassium chloride in a single dose of 5.0 Gm. abolished the arrhythmia 25 minutes later. Potassium chloride in the amount of 2 Gm. every 3 hours successfully controlled the arrhythmia for at least 6 hours. The patient was found dead 15 hours after the start of potassium chloride therapy. Autopsy was not granted.

Fig. l.-Electrocardiogram taken Mar. 16, 1956. (See text.)

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The effect of the Valsalva maneuver upon alternating bidirectional tachy- cardia has not been reported previously. Presumably the mechanism by which the Valsalva maneuver abolished the arrhythmia in this case is similar to that

induced by carotid sinus pressure which has been reported by several authors.3*4*‘0 It is interesting to note that neither left or right carotid sinus massage altered

the arrhythmia in this case. Perhaps the lack of effect of carotid sinus massage

was related to the unusually short and thick neck of the patient. The effect of potassium chloride in abolishing the arrhythmia at least tem-

porarily has been noted in previous reports. 2~3 Likewise, the frequent occurrence of digitalis intoxication in the reported instance of this arrhythmia has been noted previously.“r4 The salutary effect of potassium upon arrhythmias induced by digitalis is now well established.

In our patient, the Valsalva maneuver simultaneously abolished both the upward!y and downwardly directed complexes by reverting the rhythm to the pre-existing atria1 fibrillation. This would suggest that the focus of impulse

information responsible for the alternating bidirectional tachycardia was sus-

$‘;gr “3” ALTERNATING BIDIRECTIONAL TACHYCARDIA 443

ceptible to the influence of reflex activity, and, therefore, located supraventric- ularly. The normal time required for depolarization (0.08 to 0.09 second) for both the upward and downward complexes suggests that impulse formation arose above the level of the bifurcation of the bundle of His.

The R-R interval of the upwardly directed complexes was equal to that of the downwardly directed complexes (0.72 second). The interval between the upwardly directed complex and the succeeding downwardly directed complex was precisely 0.36 second, indicating an equal length of ventricular diastole for both the upward and downward complexes. The concept of a single focus re- sponsible for both the downward and upward complexes is favored by the finding of identical ventricular rates and identical periods of ventricular diastole.

These observations suggest that the mechanism of the arrhythmia in this case may be due to alternate conduction down the left and right branches of the bundle of His of an impulse which arises from a single focus above the level of the bifurcation of the bundle.

Since the points cited above in support of the postulated mechanism in this case are not all present in the previously reported cases, it seems reasonable to assume that more than one mechanism may operate to produce an arrhythmia with alternating upward and downward complexes. The use of the designation of “alternating bidirectional tachycardia” is suggested to exclude those cases of ventricular tachycardia with runs from multiple intraventricular foci and to avoid qualifying terms which imply a single mechanism of production.

SUMMARY

A case is reported of alternating bidirectional tachycardia in which the bene- ficial effect of the Valsalva maneuver and oral potassium chloride was demon- strated.

REFERENCES

1. 2.

Zimdahl, W. T., and Kramer, L. I.: AM. HEART J. 33:218, 1947.

3. Enselberg, C. D., Simmons, H. G., and Mintz, A. A.: AM. HEART J. 39:713, 1950.

4. Zimdahl, W. T., and Townsend, C. E.: AM. HEART J. 47:304, 1954.

5. Hellman, E., and Lind, A.: AM. HEART J. 51:140, 1956.

6. Gallavardin, L.: Arch. mal. coeur 19:153, 1926.

7. Palmer, R. S., and White, P. D.: AM. HEART J. 3:454, 1928.

8. Felberbaum, D.: Am. J. M. SC. 166:211, 1923. Schwensen, C.: Heart 9:199, 1922.

9. Luten, D.: Arch. Int. Med. 35:87, 1925. 10. Bellet, S.: Clinical Disorders of the Heart Beat, Philadelphia, 1953, Lea & Febiger, p. 208.