Left ventricular function in acute hypothyroidism: a Doppler echocardiography study.
BACKGROUND
Acute changes in cardiac parameters may occur after L-thyroxine withdrawal in patients totally thyroidectomized for thyroid cancer. The literature data regarding cardiac function in acute hypothyroidism are limited and discordant.


METHODS
In order to evaluate the effects of acute hypothyroidism on cardiac function, 20 athyreotic patients (3 males, 17 females, mean age 46.4 +/- 8.6 years, range 18-58 years) underwent Doppler echocardiography during L-thyroxine therapy (euthyroid phase) and 5 weeks after hormone therapy withdrawal (hypothyroid phase).


RESULTS
Significant changes in the left ventricular mass (83 +/- 12 vs 93 +/- 17 g/m2, p = 0.004) and end-diastolic volume (56 +/- 9 vs 50 +/- 9 ml/m2, p = 0.01) were found. Among systolic function parameters, the pre-ejection period/left ventricular ejection time (PEP/LVET) ratio (0.33 +/- 0.07 vs 0.40 +/- 0.08, p = 0.0002), aortic peak flow velocity corrected for heart rate (3.9 +/- 0.7 vs 3.5 +/- 0.5 cm/s, p = 0.02) and mean aortic acceleration corrected for heart rate (45 +/- 15 vs 38 +/- 9 cm/s2, p = 0.007) showed significant variations, whereas the left ventricular fractional shortening (39 +/- 5 vs 40 +/- 6%, p = NS) and ejection fraction (69 +/- 6 vs 68 +/- 7%, p = NS) did not change. Among diastolic function parameters, only the E-wave velocity decreased (73 +/- 17 vs 65 +/- 12 cm/s, p = 0.01); no significant modification was found in the A-wave velocity (62 +/- 19 vs 58 +/- 14 cm/s, p = NS), E/A ratio (1.2 +/- 0.5 vs 1.1 +/- 0.3, p = NS), isovolumic relaxation time (93 +/- 16 vs 95 +/- 37 ms, p = NS) and E-wave deceleration time (233 +/- 48 vs 235 +/- 45 ms, p = NS). The pattern of left ventricular filling remained unchanged, except in 2 patients. The Suga-Sagawa's index, a known parameter of myocardial contractility, was unchanged (5.6 +/- 2 vs 6.1 +/- 2 mmHg/ml, p = NS). The systemic vascular resistance increased (1511 +/- 599 vs 2216 +/- 408 dynes-s-cm(-5), p = 0.002), while the stroke index (39 +/- 8 vs 33 +/- 7 ml/m2, p = 0.001) and cardiac index (2.74 +/- 0.6 vs 2.07 +/- 0.5 l/min/m2, p = 0.0001) significantly decreased.


CONCLUSIONS
Acute hypothyroidism was associated with left ventricular systolic dysfunction, probably due to pre- and afterload alterations rather than to an impaired myocardial contractility. The diastolic function was not significantly modified. An increase in cardiac mass was also found, possibly a consequence of early interstitial myxedema. Unlike the PEP/LVET ratio, both the fractional shortening and ejection fraction may be unreliable indicators of left ventricular systolic dysfunction in patients with acute hypothyroidism.
Di Paola
Roberto
R
Operative Unit of Cardiology, Department of Internal and Specialistic Medicine, "Garibaldi" Hospital, Catania, Italy. dipaolaroberto@tiscali.it
Alagona
Corradina
C
Pezzino
Vincenzo
V
Mangiameli
Salvatore
S
Regalbuto
Concetto
C
D000208:Acute Disease; D000293:Adolescent; D000328:Adult; D015150:Echocardiography, Doppler; D005260:Female; D006439:Hemodynamics; D006801:Humans; D007037:Hypothyroidism / Q000150:complications* / Q000188:drug therapy; D008297:Male; D008875:Middle Aged; D013974:Thyroxine / Q000008:administration & dosage; D018487:Ventricular Dysfunction, Left / Q000000981:diagnostic imaging* / Q000209:etiology*
D013974:Thyroxine