Respiratory changes of superior vena cava flow velocity in old myocardial infarction with severe left ventricular dysfunction

The clinical significance of the flow velocity of the superior vena cava (SVC) in old myocardial infarction (OMI) with severe left ventricular dysfunction were evaluated using pulsed Doppler echocardiography. The subjects consisted of 10 patients with OMI (averaged left ventricular ejection fraction: 0.37 +/- 0.11) and 10 age-matched normal controls. Among the patients, eight had extensive anterior infarction and two had both anterior and inferior infarctions. During normal respiration, the peak SVC flow velocities in systole (S) and diastole (D), and the D/S ratio were measured. To evaluate right ventricular diastolic function, we measured the peak velocity across the tricuspid orifice in early diastole (rapid inflow: T-R) and the atrial contraction phase (T-A), and the ratio T-A/T-R during quiet expiration. In the normal controls, S was greater than D, both during expiration and inspiration. During inspiration, S, D and the D/S in the normal controls increased, with a greater increase in D than in S. In the patients, however, D and the D/S did not increase during inspiration. T-R was less and the T-A/T-R was greater in the patients with OMI than in the normal controls. These findings of tricuspid flow velocity revealed impaired diastolic filling of the right ventricle in patients with OMI. In conclusion, the impaired diastolic filling of the right ventricle in patients with OMI might be one of the causes of the abnormal response of the SVC flow velocity during normal spontaneous respiration.