Kazuhiko Miyaguchi

Effects of diltiazem on left ventricular diastolic behavior in patients with hypertrophic cardiomyopathy: evaluation with exercise pulsed doppler echocardiography

To estimate the effects of diltiazem on the left ventricular diastolic abnormalities in patients with hypertrophic cardiomyopathy, transmitral flow velocity during diastole was studied before and immediately after dynamic leg exercise with the pulsed Doppler technique combined with two-dimensional echocardiography. Seventeen patients with hypertrophic cardiomyopathy and 24 apparently healthy men performed bicycle ergometer exercise in the supine position with the target heart rate set at 120 beats/min. The patients with cardiomyopathy were directed to perform the exercise at the same intensity after receiving 30 to 60 mg of diltiazem, three times daily, for 1 or 2 weeks. The pattern of transmitral flow velocity in diastole had two components, one corresponding to the rapid filling phase in early diastole and the other to the atrial contraction phase in late diastole. To assess left ventricular diastolic behavior, the following variables were analyzed: peak velocity in the rapid filling and atrial contraction phases, the ratio of peak velocity in the atrial contraction phase to that in the rapid filling phase, and pressure half-time. The changes in peak velocity in the atrial contraction phase, pressure half-time and the ratio of peak velocity in the atrial contraction phase to that in the rapid filling phase with exercise differed significantly between patients with hypertrophic cardiomyopathy with no medication and control subjects. After diltiazem, the response of these variables to exercise was almost identical in the two groups. These results suggest that diltiazem can lessen the left ventricular diastolic abnormality in patients with hypertrophic cardiomyopathy on dynamic exercise of mild intensity.

Dependency of the pulsed Doppler-derived transmitral filling profile on the sampling site

In previous reports that evaluated pulsed Doppler transmitral filling, the sampling site has varied; we examined the effect of the sample volume location on Doppler measurements. Studied were 97 patients: 58 with normal echocardiograms, 20 with mitral regurgitation, and 19 with miscellaneous cardiac diseases. Transmitral filling was recorded at the mitral anulus and at the left atrial and left ventricular (LV) sides of the mitral tips. As the sample volume was moved from the mitral anulus to the LV side, the peak velocity and time-velocity integral of early diastole increased (40.6 +/- 13.8 versus 59.0 +/- 19.0 cm/sec, 5.26 +/- 1.65 versus 8.35 +/- 2.37 cm; p less than 0.001) as did those of late diastole (48.7 +/- 11.5 versus 57.5 +/- 17.0 cm/sec, 3.48 +/- 0.97 versus 4.59 +/- 1.39 cm; p less than 0.001). The late-to-early diastolic peak velocity and time-velocity integral ratios and the late-to-total diastolic time-velocity integral ratio decreased (1.33 +/- 0.51 versus 1.06 +/- 0.41, 0.71 +/- 0.24 versus 0.58 +/- 0.19, 0.40 +/- 0.09 versus 0.36 +/- 0.08; p less than 0.001). The dependency of these indices on the sampling site was in the same degree in all three groups. However, the peak filling rate normalized to mitral stroke volume (4.71 +/- 1.43 versus 4.63 +/- 1.32 l/sec; p = NS) was not influenced by the sample volume location; thus this parameter may be more reliable for assessing LV filling.

Evaluation by exercise doppler echocardiography of maintenance of cardiac output during ventricular pacing with or without chronotropic response

To examine the effectiveness of activity-initiated rate-responsive pacing, this study assessed the increases in stroke volume and cardiac output during randomized treadmill exercise in rate-responsive and fixed-rate ventricular (VVI) pacing in 10 patients. Stroke volume index and cardiac index were determined by suprasternal Doppler measurements. Compared with the findings during VVI pacing, the rate-responsive pacing was associated with (1) prolongation of exercise duration (8.0 +/- 4.0 vs 7.3 +/- 3.6 minutes, p less than 0.05); (2) greater exercise-induced positive chronotropic response (mean maximal heart rate 127 +/- 12 vs 78 +/- 15 beats/min, p less than 0.001); (3) smaller increase in stroke volume index (38 +/- 10 vs 50 +/- 11 ml/m2, p less than 0.001), and (4) greater increase in cardiac index (4.7 +/- 1.1 vs 3.9 +/- 1.0 liters/min/m2, p less than 0.001). A significant correlation was observed between age and percent increase in stroke volume index during VVI pacing (p less than 0.05). These findings indicate that VVI pacing increased stroke volume more than did rate-responsive pacing, especially in younger patients, but the increase in cardiac output was less than that seen with rate-responsive pacing due to the absence of chronotropic response. Accordingly, an activity-sensing, rate-responsive pacemaker can effectively increase the heart rate, significantly augment cardiac output and extend the duration of exercise.

Characteristic findings on the standard 12-lead ECG in patients with the fasciculoventricular Mahaim fiber

Standard 12-lead electrocardiograms with a Q wave in lead V1 were obtained from 32 subjects without organic cardiac disease and analyzed for features that might characterize an abnormal atrioventricular conduction through the fasciculoventricular Mahaim fiber. Following an infusion of ajmaline, the Q wave in V1 vanished abruptly and changed to an rS pattern in the 12 ajmaline responders. Discriminant analysis was performed to distinguish the ajmaline responders from the others. The explanatory variables were number of precordial leads with the abnormal Q wave, existence of the septal q waves, existence of the slurring of the Q wave in V1, existence of clockwise rotation, and existence of high voltage (RV5 + SV1 > 3.5 mV). Three variables, the absence of the septal q waves, the presence of the slurring, and the absence of clockwise rotation, were found to predict a positive response to ajmaline (discriminant probability = 77%). These findings associated with the Q wave in V1 suggest that the fasciculoventricular fiber may be present.

Left ventricular function in asthmatic children chronically treated with theophylline evaluated by exercise Doppler echocardiography

To evaluate the chronic effects of theophylline on cardiac function, M-mode and pulsed Doppler derived variables were measured at rest and the suprasternal continuous wave Doppler measurement of ascending aortic flow was used during treadmill exercise testing. Subjects consisted of 13 children with stable asthma (mean 11.7±2.2 years) who were treated with theophylline for at least one year and 16 age-matched, untreated normal volunteers. In the resting state, the chronic administration of theophylline seemed to produce a slight increase in percent fractional shortening, outflow peak velocity and atrial contribution to ventricular filling in the asthmatic children as compared to normals, but these changes were not statistically significant. The asthmatic children showed significantly lower values than the controls in exercise induced changes in the peak velocity, stroke index and cardiac index, but not in the heart rate. Therefore, chronic administration of theophylline appears to have a minimal effect on resting cardiac function, but a possibly deleterious effect on the cardiac response to exercise testing.

Continuous wave Doppler echocardiographic evaluation of cardiac output and its applications to treadmill exercise

To evaluate the clinical usefulness of Doppler-derived cardiac output and the effect of altered left ventricular function during maximal treadmill exercise, this study was performed using continuous wave (CW) Doppler technique through the suprasternal notch acoustic window. Subjects consisted of 22 patients with coronary artery disease (study 1) and 21 healthy male volunteers (study 2)

Influence of left ventricular preload reduction by hemodialysis on the Doppler-derived left ventricular filling profile

Hemodialysis caused an average 3.2-liter volume loss, but blood pressure and heart rate did not change significantly. Hemodialysis diminished the left atrial dimension (35±5 to 31±5 mm; p>0.001), indicating that it reduced left ventricular preload. These results indicate that the atrial contribution to ventricular filling was more effective afterwards than before hemodialysis and that under depressed left ventricular diastolic function, the atrial contribution decreased as preload increased further

Effects of Vasodilators on Venous Tone in Vivo in Dogs

The authors investigated, in vivo, the effects of four vasodilators on venous tone in dogs. Baseline venous tone was determined from the pressure: diameter relationships in the inferior vena cava (VSIVC) and femoral vein (VSFV) as measured during several seconds of occlusion of the proximal inferior vena cava. All of the slopes were nearly linear. All vasodilators were adminstered in dosages sufficient to lower blood pressure by approximately 20%; these dosages also decreased systemic vascular resistance by 15% to 30%. Isosorbide dinitrate reduced VSIVC from 7.17 ± 0.81 to 5.81 ± 0.73 mmHg/mm and VSIVC from 59.4 ± 13.5 to 37.2 ± 6.6 mmHg/mm. Neither nifedipine nor nisoldipine altered VSIVC or VSFV. However, prazosin decreased VSIVC from 13.2 ± 3.3 to 10.7 ± 2.7 mmHg/mm and VSFV from 43.5 ± 11.3 to 29.9 ± 8.8 mmHg/mm. These results suggest that isosorbide dinitrate and prazosin decrease venous tone in vivo, whereas nifedipine and nisoldipine do not.

Evaluation of left atrial rhythm with pulsed Doppler echocardiography.

SummaryTo evaluate the origin of ectopic atrial rhythms, the beginning of atrioventricular inflow due to left and right atrial ejection was estimated using the pulsed Doppler combined with two-dimensional echocardiography. In ten normal controls, the beginning of transtricuspid flow due to atrial ejection preceded that of transmitral by 0 to 40 msec with an average of 22 msec. In contrast, the beginning of right atrial ejection flow lagged behind that of left atrial by 40 to 80 msec in case 1 and by 20 to 50 msec in case 2 of ectopic atrial rhythm. The significant delay of atrioventricular inflow due to right atrial ejection in these two patients strongly suggests that the ectopic atrial rhythm is of left atrial origin. The pulsed Doppler echocardiography is considered to be a useful clinical tool for noninvasive evaluation of the left atrial rhythm.