Correlation between initial potentials on a signal-averaged P-wave and indice of electrophysiologic measurements in the right atrium.

The aim of this study was to determine whether initial potentials of the P-wave on a signal-averaged electrocardiogram (SAE) during sinus rhythm reflect indices of electrophysiologic measurements in the high lateral right atrium. A total of 67 patients underwent P-wave signal averaging during electrophysiologic testing. The correlation between root mean square voltages for the initial 10 and 20 msec of the P-wave on the SAE and indices of electrophysiologic measurements, sinus node recovery time (SRT) and sinoatrial conduction time (SACT), obtained from programmed stimuli, was evaluated. It was found that the initial potentials of the P-wave on the SAE correlated negatively with SRT and SACT (-0.37 < or = r < or = -0.30). It was concluded that the initial potentials correlated with indices of electrophysiologic measurements, although the statistical significance was weak.

Use of the body surface recovery time for detection of coronary artery disease.

We explored the relationship between body surface recovery time (RT), the interval between the QRS onset and the time of maximum derivative in the T-wave on a 16 precordial lead system electrocardiogram (ECG), and monophasic action potential (MAP) duration of the left ventricular endocardium in 9 patients in whom electrophysiologic testing was indicated. The usefulness of RT measurement on body surface ECG for the detection of coronary artery disease was evaluated in 98 patients who had chest pain. The RT located in the right clavicular or upper sternal area showed a very high positive correlation (r = 0.91, p < 0.001) with MAP duration from the left ventricular endocardium and showed specific shortening in patients with one-vessel disease of the left anterior descending coronary artery. With a criterion of the RT located in the right clavicular or upper sternal area corrected by Bazett's formula < 380 msec1/2, a sensitivity of 81% and a specificity of 80% were achieved for detection of one-vessel disease of the left anterior descending coronary artery.

[Evaluation of sinoatrial conduction by the initial potential of the P wave signal-averaged electrocardiogram].

We investigated whether sinoatrial conduction can be evaluated by the initial potential (IP) on the P wave signal-averaged electrocardiogram (PSAE). We studied 61 patients who underwent electrophysiologic study. Programmed stimulation was performed to obtain the sinoatrial conduction time (SACT) and the maximal sinus node recovery time (SRTmax). The root mean square voltages for the initial 10 and 20 msec of the filtered P waves (IP10 and IP20) were calculated based on PSAE. The association between IP10 and IP20 with SACT or SRTmax was analyzed by linear regression analysis. The reduction of IP10 or IP20 was negatively correlated with the prolongation of SACT, but was not correlated with the prolongation of SRTmax. Our findings showed that IP on the PSAE can be used to estimate the status of sinoatrial conduction.

[The utility of body surface isochrone mapping of recovery time in diagnosing effort angina].

Myocardial ischemia is characterized by ST depression on a standard electrocardiogram caused by shortening of the action potential duration (APD). We investigated whether shortening of the APD can be used as a screening criterion, in place of ST depression, to diagnose effort angina. Estimation of APD was made based on recovery time (RT) on a 16-lead system signal-averaged electrocardiogram (SAE). RT was defined as the interval between the onset of the QRS complex and the maximum positive value during the T wave of SAE. The values of RT measured at each lead were plotted on a graph to produce an electrocardiographic isochrone map. RT were significantly shortened in all electrocardiographic leads in patients with effort angina. Shortening in RT was especially marked in the right precordal leads and was shown to be a highly specific criterion for screening effort angina.

The first report of a case with acute myocardial infarction showing familial deficiency of creatine kinase.

A 46-year-old male patient was diagnosed as suffering from acute myocardial infarction, but his serum creatine kinase (CK) level was extremely low and no CK isozymes were detected in the serum. The total CK activities in the skeletal muscle amounted to only 2% of that of the control. Electrophoresis of the CK isozymes in the skeletal muscle showed that CK-MM was absent but the CK-BB and abnormal isozyme bands were present. There was no evidence of myocardial ischemia, although the exercise treadmill test revealed ST segment depression in the chest leads. One of the patient's sisters had an extremely low serum CK level suggesting inheritance of this abnormality. This is the first report of a case showing familial deficiency of CK.

Stimulative effect of sodium nitroprusside on peristaltic reflex in isolated guinea pig ileal segments.

Intestinal segments obtained from guinea pig ileum were set up in an organ bath to record peristaltic responses to distension by a pressure rise in the lumen. The effects of drugs applied in the bathing medium on the peristaltic responses were examined. Sodium nitroprusside (10(-9) M to 10(-5) M) stimulated the peristaltic reflex. Nitroglycerin (10(-7) M) was similarly effective in stimulating the peristalsis. A permeable cyclic GMP, 8-bromo cyclic GMP (2.5 x 10(-4) M), mimicked the action of these compounds. Methylene blue (10(-5) M) blocked the nitroprusside-induced stimulation of the peristalsis, but not the effect of 8-bromo cyclic GMP. Sodium nitroprusside did not change the baseline tension of the circular muscle, and it enhanced neither the contractile response to electrical direct stimulation nor the cholinergic transmission to the circular muscle. These results suggest that nitric oxide is formed from the nitrocompounds in mechanosensitive neurons in the intestine and causes activation of guanylate cyclase by which the level of intracellular cyclic GMP is elevated, and cyclic GMP acts to make the stretch receptors more sensitive. As nitric oxide is derived from the enteric vascular bed or neurons, its importance as a modulator of peristaltic activity in the intestine is discussed.