Left ventricle filling abnormalities prior to and following treatment of thyrotoxicosis -- is diastolic dysfunction implicated in thyrotoxic cardiomyopathy?

Despite cardiac failure being a well recognised complication of thyrotoxicosis, systolic function has generally been reported as maintained or enhanced. In this study, left ventricular diastolic function was assessed in 16 thyrotoxic patients and 18 age-matched controls by pulsed-Doppler echocardiography. Patients were re-studied after 3 and 12 months of treatment. Prior to treatment all standard Doppler-derived indices of diastolic function were significantly different to control (isovolumic relaxation time (IVRT) 63+18-9 vs 84-0+14-8 ms, peak early filling velocity (E max ) 79-2+15-2 vs 61-9+ 10-7 cm . s~',peak atrial filling velocity (A max ) 68-2 17-9 vs42-29-4 cm . s~', deceleration of early filling (EjF slope) 6-1 + 1-8 vs3-7+ 1-1 m . s' 1 , thyrotoxic vs control). However, these filling abnormalities appear likely to reflect the tachycardia and reduced systemic vascular resistance (SVR) found in the patients (heart rate 102+15 vs 76 + 9, SVR 874 + 207 vs 1293 362 dynes .s~'. cm~5, both P < 0001). After 3 months of treatment haemodynamics were similar in the two groups but filling remained abnormal in patients with a pattern suggesting increased transmitral pressure gradients (E max 73-1 + 15-1 cm.s~'', A max 55-8 + 19-2cm.s~', E/F slope 4-9 + 2-0m . s~',all?< 005 compared to controls). After 12 months of treatment most parameters had returned to normal but the atrial contribution to left ventricular filling remained high ( A max 54-7 + 13-9 vs control 42-2 + 9-4 cm . s~' .flow velocity integral of atrial filling 4-7 + 1-3 vs 3-6+11 control, both P<001). Left ventricular filling is therefore highly abnormal before and during the treatment of thyrotoxicosis. However, these changes appear unlikely to reflect an intrinsic thyrotoxic cardiomyopathy and are more likely to represent a combination of prolonged increases in left ventricular filling pressures along with abnormalities of left atrial function. The abnormal Doppler parameters emphasise the importance of sinus rhythm in maintaining left ventricular filling in thyrotoxicosis and may explain why marked haemodynamic deterioration may result from the development of atrial fibrillation in these patients.