Assessment of serum flecainide trough levels in patients with tachyarrhythmia.

The reported therapeutic range for trough flecainide concentration is 200-1000 ng mL(-1). Severe adverse events, such as ventricular arrhythmias, have occurred occasionally in patients whose serum flecainide exceeded 1000 ng mL(-1). However, the lower limit remains controversial. We have evaluated blood flecainide concentrations in patients with tachyarrhythmia who received the drug to control palpitation. We measured the flecainide trough levels and incidence and frequency of palpitation of 44 outpatients receiving oral flecainide (150-300 mg daily). Mean serum flecainide trough concentrations differed significantly between patients with (n = 14) and without (n = 30) palpitation (259.5 +/- 85.2 vs 462.2 +/- 197.7 ng mL(-1), P < 0.01). The frequency of palpitation decreased as the serum flecainide concentration increased. The incidence of palpitation was 65% at serum flecainide concentrations < 300 ng mL(-1) and 11% at > or = 300 ng mL(-1). QRS values were increased significantly in patients with serum flecainide < 300 ng mL(-1) compared with > or = 300 ng mL(-1) (0.110 +/- 0.016 s vs 0.093 +/- 0.019 s, P < 0.05). We concluded that to control paroxysm in patients receiving flecainide for tachyarrhythmia serum flecainide concentrations should be maintained at > or = 300 ng mL(-1).

Assessment of propagation velocity by contrast echocardiography for standardization of color Doppler propagation velocity measurements.

BACKGROUND: Color Doppler propagation velocity (Vp) (color-Vp) has not yet been standardized, although it should be able to specifically reflect the intraventricular movements of left ventricular (LV) inflow. Because contrast echocardiography can depict a specified flow, we used this modality to standardize measurements of color-Vp of LV inflow. METHODS: We performed contrast echocardiographic examinations in 100 patients (70 men, 30 women; age 53 +/- 12 years). Four types of color-Vp were measured: by the flow wave front method and by aliasing method using 3 aliasing velocity levels based on the peak velocity of early diastolic flow of transmitral flow. We also determined contrast echocardiographic Vp by M-mode imaging of LV inflow (contrast-Vp). RESULTS: Contrast-Vp and all 4 types of color-Vp could be compared in 86 patients. Contrast-Vp was significantly lower than color-Vp ( P < .01), except for color-Vp measured at the aliasing level 50% > peak velocity of early diastolic flow >/= 40% (color-Vp 40). A close relationship was observed between contrast-Vp and color-Vp 40 ( r = 0.801, P < .0001). Contrast-Vp and color-Vp 40 showed high ability to detect abnormal transmitral flow patterns according to receiver operating characteristics curves (area under curve for contrast-Vp, 0.94; for color-Vp 40, 0.90). CONCLUSIONS: Our results should be useful in standardization of color-Vp measurement to specifically reflect propagation of the fluid elements derived from LV inflow, with ability to distinguish LV filling abnormalities.