Blood-pressure-lowering effect of a novel fermented milk containing gamma-aminobutyric acid (GABA) in mild hypertensives

OBJECTIVE

To study the effect of a new fermented milk product containing GABA (FMG) on the blood pressure (BP) of patients with mild hypertension.

DESIGN

A randomized, placebo-controlled, single-blind trial.

SETTING

The study was carried out at the outpatient clinic of the Cardiovascular Disease Center, Tokyo Metropolitan Police Hospital, Japan.

SUBJECTS

The study population comprised 39 mildly hypertensive patients (16 women and 23 men) aged 28-81 y (mean, 54.2 y).

INTERVENTIONS

The study consisted of a 12-week period of daily intake of FMG or placebo (weeks 1-12) followed by 2 weeks of no intake (weeks 13 and 14). We measured the peripheral BP and heart rate of seated patients at weeks 0, 2, 4, 8, 12 and 14. Routine blood study and urinalysis were performed before and after the intake.

RESULTS

There was a significant decrease of BP within 2 or 4 weeks, and it remained decreased throughout the 12-week intake period. For the FMG recipients, the mean decrease after 12 weeks was 17.4+/-4.3 mmHg in the systolic BP (SBP) and 7.2+/-5.7 mmHg in the diastolic BP (DBP). Both of these values differed statistically from baseline levels (P<0.01), and the SBP of the FMG group differed from the placebo group (P<0.05). Heart rate, body weight, hematological and blood chemistry variables, and urinalysis results (glucosuria and proteinuria) did not vary both groups throughout the study.

CONCLUSION

FMG may contribute to lowering BP in mildly hypertensive people.

High-performance liquid chromatographic determination of hippuric acid in human urine

A method is described for the determination of urinary hippuric acid by high-performance liquid chromatography. The method used ethyl acetate extraction for partial clean up of the urine. The separation was carried out on a reversed-phase column using 20% methanol in 0.01 M aqueous potassium phosphate containing 0.5% acetic acid as a mobile phase. The column effluent was monitored with a UV detector at 254 nm. Hippuric acid was separated from other normal urine constituents in less than 10 min. Metabolites of xylene and styrene did not interfere with the assay. Analytical recoveries from urine were excellent and peak height and concentration were linearly related.

Relation between the size of lesions and arrhythmias produced by microwave catheter ablation with a special electrode device

The purpose of this study was to examine the effects of microwave catheter ablation of ventricular myocardium. Microwave energy with a frequency of 2450 MHz was delivered via a coaxial catheter with an electrode ball tip. Microwave energy was applied to canine isolated left ventricular endocardium in vitro and to 6 anesthetized dogs in vivo at 50 watts for 15-150 sec. Ventricular arrhythmia was not observed during ablation in any of the dogs when microwave energy was applied for less than 45 sec. When the duration of microwave ablation was greater than 45 sec, ventricular premature contractions were observed in all of the dogs. Nonsustained ventricular tachycardia developed when the duration of microwave delivery was greater than 90 sec. After the cessation of ablation, ventricular arrhythmias did not occur and ventricular programmed stimulation did not induce ventricular tachycardia in any of the dogs. Except for ventricular arrhythmia, no declines in the hemodynamic status were observed in any of the 6 dogs. The size of the ablated lesion was significantly greater as the duration of ablation was increased (p < 0.05). When ablation lasted for more than 120 sec, the coagulation layer was extended to the epicardium in all 6 dogs. The results of this study suggest that microwave ablation is feasible for the treatment of tachyarrhythmias from deep focus of ventricular myocardium with relatively small proarrhythmic effects.

Effect of radiofrequency catheter ablation of the slow pathway on the atrioventricular node

Although the effective refractory period (ERP) of the fast pathway is reported to be shortened after radiofrequency catheter ablation of the slow pathway in atrioventricular nodal reentrant tachycardia (AVNRT), whether the atrioventricular (AV) nodal physiology maintains the same condition over the long term is controversial. To assess the AV nodal physiology after catheter ablation of the slow pathway in AVNRT, the A-H interval and ERP of the fast pathway were measured before, immediately after and 3 months after catheter ablation in 12 patients. We compared these factors in 12 patients with left concealed accessory bypass tract to clarify the mechanism of the electrophysiological change in the AV node. Both the A-H interval and ERP of the fast pathway were significantly shortened from 111 +/- 18 to 96 +/- 17 ms and 365 +/- 68 to 261 +/- 52 ms immediately after catheter ablation (p < 0.01), and recovered to 128 +/- 44 and 372 +/- 80 ms 3 months after catheter ablation. There were no significant differences in the A-H interval of the fast pathway between the period immediately after and 3 months after catheter ablation following administration of atropine sulfate (99 +/- 52). There were no significant differences in the ERP of the fast pathway between the period immediately after and 3 months after catheter ablation following administration of atropine sulfate (248 +/- 33 ms). On the contrary, there were no significant changes in the A-H interval and ERP of the AV node at these two times in patients with Wolff-Parkinson-White (WPW) syndrome. The change in characteristics of AV nodal physiology was observed only immediately after catheter ablation in AVNRT, but not in WPW syndrome. The change in electrophysiology immediately after catheter ablation was similar to that following administration of atropine sulfate in AVNRT 3 months after catheter ablation. These findings suggest that catheter ablation does not cause a permanent change in AV nodal physiology and that the location of the ablated site plays an important role in AV nodal physiology.

Assessment of atrioventricular nodal electrophysiological characteristics after radiofrequency catheter ablation of the slow pathway in atrioventricular nodal reentrant tachycardia--3-month follow up

Radiofrequency catheter ablation of the slow pathway is commonly used to treat atrioventricular (AV) nodal reentrant tachycardia. However, there has been little study of the follow-up assessment of AV nodal physiology. We compared AV nodal electrophysiological characteristics before, immediately after, and again 3 months after successful catheter ablation in 17 patients (mean age 50 +/- 16 years). Sinus cycle length, Wenckebach cycle length, A-H interval at a paced cycle length of 600 ms, effective refractory period and functional refractory period of the fast pathway were significantly changed immediately after catheter ablation, but had recovered 3 months after the procedure. There were no significant differences between the electrophysiological parameters immediately after catheter ablation and those 3 months after the procedure under the intravenous injection of atropine sulfate. We conclude that, due to changes in autonomic nervous tone, AV nodal electrophysiological characteristics are influenced immediately after catheter ablation of the slow pathway in AV nodal reentrant tachycardia.

Cost effectiveness of radiofrequency catheter ablation versus medical treatment for paroxysmal supraventricular tachycardia in Japan

This study evaluated the cost of performing radiofrequency catheter ablation in Japanese patients with paroxysmal supraventricular tachycardia refractory to antiarrhythmic drug therapy in comparison with the cost of continuing pharmacologic treatment. Twenty patients (mean age 44 +/- 14 years) underwent successful ablation: 15 patients with Wolff-Parkinson-White syndrome and five with atrioventricular nodal reentrant tachycardia. The mean duration of symptoms was 77 +/- 60 months. The patients had been treated with 2.6 +/- 1.7 antiarrhythmic drugs before undergoing ablation. Charges derived from hospital bills were compared with the outpatient charges for the year before ablation. The mean hospital stay for the ablation procedure was 4.3 +/- 0.5 days. The mean total charge for ablation was 982,806 yen +/- 103,195, and 5.7 +/- 0.7 times the outpatient charges in the previous year. The majority of radical cure charges were the costs of the electrode catheters used in the ablation procedure. All patients had a successful outcome and required no additional antiarrhythmic drug therapy. If medical treatment were continued without ablation, the mean total life-expectancy charges were estimated at 7,064,726 yen +/- 3,116,621, 41.0 +/- 19.2 times the outpatient charges. The total life charges of medical treatment were significantly more than the total ablation charges (p < 0.001). This study suggests that radiofrequency catheter ablation is of clinical benefit in treating paroxysmal supraventricular tachycardia, and markedly reduces the cost of definitive therapy. This strategy appears to be more economical than pharmacologic treatment.

Pharmacodynamic characterization of posture-related diuretic and saluretic responses to furosemide in humans

To characterize the postural effect on the pharmacodynamic response to furosemide, seven healthy female subjects received the drug (30 mg i.v.), and the diuretic response and urinary drug excretion were monitored either in the supine or upright posture more than 5 h after dose. Six days later the same procedure was repeated, each subject being assigned to the other posture. Diuresis, chlor- and natriuresis were about 50% greater (P less than .01) in the supine than in the upright posture up to 45 min after dose, despite no significant difference in urinary drug excretion between the postures. Creatinine clearance and fractional sodium excretion were also significantly (P less than .05) greater in the supine posture. Pharmacodynamic analysis with the Emax model revealed that the maximum drug response (Emax) to furosemide in the upright posture was significantly (P less than .01) attenuated by about 65% of that in the supine posture, with no significant difference in either ER50 (urinary drug excretion rate producing 50% of Emax) or slope between the postures. Plasma norepinephrine concentration was significantly (P less than .05) greater, whereas urinary kallikrein excretion was significantly (P less than .05) less in the upright posture. There were no significant differences in blood pressure, plasma renin activity and atrial natriuretic peptide as well as in urinary excretion of prostaglandin E2, dopamine and adenosine between the postures.(ABSTRACT TRUNCATED AT 250 WORDS)

[The influence of repetitive delivery of radiofrequency current in catheter ablation]

The single delivery of radiofrequency current to the cardiac tissue can produce discrete small and shallow area of homogeneous coagulation necrosis. Little is known, however, concerning the influence of repetitive deliveries of radiofrequency current to the identical site of the ventricular myocardium. Therefore, in animal experiments using 8 dogs, we investigated the influences of those applications on the ventricular myocardium from the histological and electrocardiographical aspects. The used frequencies of radiofrequency current were 13.56 MHz (RF-50), 520 kHz (Hatt 200 S) and 500 kHz (LL-50). Released power was 25 Watts in current and 20 seconds in duration. The innings of application were 10, 20 and 30 times per one ablation session. The depth of ablated lesion became greater as the applied innings increased in any generator of radiofrequency current. The ablated lesion by the delivery over 20 times reached from the ventricular endocardium to the epicardium. In contrast, surface area produced by repetitive application was determined by the size and length of the tip of electrode catheter. T wave inversion and isolated premature ventricular contraction on electrocardiogram were observed only during repetitive radiofrequency energy application. Thus, since the repetitive delivery of radiofrequency energy to the identical myocardium caused the deep ablated lesion reached to the epicardium, caution should be taken against myocardial perforation in a clinical setting. However, this application could be useful for the ablation of deeper lesion responsible for ventricular tachycardia.

[An experimental study of catheter ablation using microwave energy via coaxial electrode catheter]

The purpose of this study was to examine the efficacy, arrhythmogenicity, and the size of ablated lesions of catheter ablation with microwave energy. Microwave energy generated by a device with a frequency of 2450 MHz, was delivered via a bipolar electrode coaxial catheter with an electrode ball tip. Microwave ablation was applied (50 watts for 15-150 sec.) on the left ventricular endocardium in 6 dogs. No ventricular arrhythmia occurred during ablation in any of the dogs when microwave catheter ablation was applied for less than 45 sec. However, when the duration of microwave catheter ablation was longer than 45-60 sec, ventricular premature contractions were observed in all 6 dogs. When ablation time was set for a longer time, the dogs developed nonsustained ventricular tachycardias. Nevertheless, ventricular arrhythmias after ablation did not occur in all dogs. Ventricular programmed stimulation after ablation did not induce ventricular tachycardia in any of the dogs. When ablation time lasted more than 120 sec, the coagulation layer was extended to the epicardium in all 6 dogs. The results of this study suggest that microwave ablation is feasible for the treatment of tachyarrhythmias from a deep focus of the ventricular myocardium.