Electrophysiologic Factors Responsible for the Induction of AV Nodal Reentrant Tachycardia / 대한내과학회지

OBJECTIVES: Although a subtle balance between conduction time of the antgrade slow pathway and refractory period of the retrograde fast pathway is known to play the most critical role in the induction of AV nodal reentrant tachycardia(AVNRT), other electrophysiologic factors such as concealed conduction in to the fast pathway have been suggested to be responsible. The present study was performed to determine the electrophysiologic factors responsible for the induction of AVNRT. METHODS: Total 34 subjects undergoing electrophysiologic study(EPS) including 9 normal subjects(SAVNP), 7 subjects with dual AV nodal pathways(DAVNP) but no inducible AVNBT, and 18 inducible AVNRT patients were included in this study. EPS was performed using the conventional technique. To evaluate the presence of concealed conduction into the fast AV nodal pathway(FP) and its effects on the effective refractory period(ERP) of the FP (FP-ERP) to a subsequent impulse, single(A2) and double atrial extrastimuli(A2A3) were given. FP-ERP of conducted A2 [FP-ERP-A2(+)] was measured with a second atrial extrastimulus(A3) following a first atrial extrastimulus(A2), which was delivered at a coupling interval 20-30ms longer than FP-ERP. ERPs of non-conducted A2 [FP-ERP-A(-)] was measured with A3 following A2 at coupling intervals 20 ms shorter than FP-ERP. Concealed conduction was considered to be present when A1A3 interval of A3 blocked at the FP with a longest A2A3 interval was longer than FP-ERP. Concealment index(CI)-1 and CI-2 were calculated by dividing FP-ERP-A2(-) by FP-ERP-A2(+) and FP-ERP, respectively. In addition, relationship between antegrade slow pathway conduction time(A2H2) and retrograde fast pathway conduction time(HA), retrograde AV conduction system block cycle length(VA-BCL), and retrograde AV conduction system EBP(VA-ERP) was evaluated by a regression analysis. RESULTS: Concealed conduction was present in all the subjects. CI-1 was 0.63 +/- 0.04 and CI-2, 0.79 +/- 0.04 in SAVNP and 0.67 +/- 0.11, 0.68 +/- 0.07 respectively, in AVNRT patients in whom the antegrade slow pathway(SP) was ablated with catheter ablation, showing no significant difference in CI between 2 groups. At the time of induction of AVNRT with A2, A2H2. was significantly correlated with FP-ERP and FP-CT(r=OA43, p=0.04; r=0.507, p=0,02, respectively). By multivariate regression analysis, it was derived that A2H2 should be greater than "0.79 FP-ERP+1.57 FP-CT-0.44 HA-190(ms)" (r=0.71, p<0.05). CONCLUSION: Induction of typical AVNRT with A2 is determined by conduction time of the slow pathway, refractory period and conduction velocity of the fast pathway, and concealed conduction into the fast pathway.

Clinical Effect of Penbutolol(Betapressin(R))on Hypertensive Patients

The only clinically avilable levo-isomer type of beta-recepter blocker is penbutolol sulfate, and it is already accepted as one of beta-receptor blockers for initial antihypertensive drug therapy according to the report of 1988 Joint National Committee on Detection, Evaluation, and Tratment of High Blood Pressure. To evaluate the antihypertensive efficacy, effect on the quqlity of life, and side effects of penbutolol recently introduced into Korea, penbutolol was administered to 29 essential hypertensive(mild 9, moderate10, and severe 10) patients for 12 weeks or longer. The result of the clinical analysis are as follows; 1) The mean age was 50.0+/-10.9(M+/-SD), and the sex distribution between male and female was16:13. 2) The blood pressure lowering effects of penbutolol as a monotherapy were marked in 16, moderate in 6, and insignificant in 2 cases. The systolic blood pressure was significantly decreased from 179.1+/-20.2 to 135.4+/-16.5mmHg(P<0.005), and the diastolic blood pressure from 112.6+/-13.5 to 84.0+/-11.9mmHg(P<0.005)after 12 weeks' penbutolol therapy. 3) The heart rate was significantly decreased from70.3+/-13.3 to 65.5+/-9.1 per minute(P<0.05). 4) The quality of life was improved markely in 5(17.2%) and slightly in 8 cases(29.6%). 5) There were no significant laboratory changes after 12 weeks' penbutolol therapy. 6) Two out of three cases with non-specific ST segment and T wave changes in EKG and two out of 9 cases with EKG were normalized, 2 cases of LAH with strain were improved. 7) The side effects of penbutolol were dizziness in 4, sexual dysfunction in 2, and skin rash in 1 case. 8) Final multifarious assessment of penbutolol therapy showed that it was very useful in 11(37.9%), useful in 4(13.8%) and slightly useful in 7 cases(24.1%). These reult suggest that penbutolol is a first-line antihypertensive agent with an effective antihypertensive action, improving quality of life, with no significant laboratory changes and few side effects.

A Case of Recurrent Pacemaker Twiddler's Syndrome

Pacemaker twiddler's syndrome is reported as a very rare complication of permanent pacemaker implantation. There was a recent report suggesting that the incidence of pacemaker twiddler's syndrome increase recently presumably as a result of the implantation of thinner and smaller pacemaker system than before. We experienced a case of pacemaker twiddler's syndrome complicated 3 times with the conventional method of implantation or replacement during 14 months after the first implantation(Optims MP 158C and Pacing lead 400, Telectronic)on June 13th 1987. This case was an 18 year-old high school girl who had suffered frequent syncope for 2 years and extertionl dyspnea for 5 years due to congenital complete heart block, of which block site was proved to be AV nodal by His bundle electrogram. Pacemaker twiddler's syndrome developed 3 times;firstly 6 weeks after the first implantation in the right subclavicular fossa, secondly 10 weeks after the replacement of the twisted pacing lead, thirdly 10 months after the change of implantation site to the left subcalvicular fossa with the replacement of the twisted and fractured lead. Finally, the pacemaker generator was anchored to the clavicular periostium and pectoralis fascia at several points by using Dacron pouch.

A Clinical Study for the Captopril Effects on Hypertensive Patients

Catopril, an angiotensin converting enzyme inhibitor, was administrated in 30 hypertensive patients(mild 8, moderate 12, severe 10 cases)for 12 weeks or longer in order to observe the hypertensive effects. Changes in quality of life, side effects, electrocardiogram and left ventricular mass index(LVMI) by 2D-guided M-mode echocardiography were also evaluated before and after captopril. 1) After 12 weeks treatment with 25 to 150mg of captopril alone, blood pressures were lowered markedly in 16(53%), moderatly in 5(17%) and midly in 2(7%), while the addition of 25mg hydrochlorthiazide to captopril in the patients who showed no satisfactory responses the blood pressure were lowered markly in 21(70), moderately in 6(20%) and mildly 3(10%) out of 30 patients studied. The average of blood pressure of the 30 subjects were systolic 180.7+/-20.7mmHg(M+/-SD) and diastolic 113.2+/-12.5 before treatment, which were lowered to 148+/-15.8 and 92.5+/-8.0mmHg respectively after 12 weeks(P<0.005). 2) Heart rates were not changed with captopril and/or hydrochlorothiazide. 3) Quality of life improved markedly in 5(17%) and slightly in 12(40%) out of 30 subjects. 4) Complete blood cell count, urinalysis and serum enzymes followed revealed no significant changes. 5) By electrocardiographic follow-up studies 1 out of 13 subjects with LVH, 1 out of 4 LAH, 1 out of 2 ST-T changes were revealed to improved to normal. 6) In 25 out of 30 cases left ventricular mass indices(LVMI) were above 125g/m2 before treatment, among which 15 cases were followed with satisfactoriness good quality of the echocardiographic recorings and the LVMI was reduced from 169.6+/-40.7 to 141.7+/-40.9g/m2(P<0.01). 7) Undesirable side effects were dry cough 3, skin rash 2, dysgeusia 1 and renal dysfunction 1. 8) Considering the blood pressure lowering effects, life quality changed and side effects together the captopril was considered very useful in 8(27%) and useful in 16(53%) out of 30 subjects. Above results suggest that captopril can be prescribed as an effective initial single agent or with in combinations with thiazide for the treatment of hypertensive of various severities with acceptably low side effects.

The Evaluation of the Left Ventricular Diastolic Function in the Patients with Essential Hypertension by Phonocardiogram and Doppler Echocardiogram

There is no doubt that the diastolic dysfunction of the left ventricular plays an important role in the pathophysiogy of clinical heart faliure in some patients, if not all, and that many hypertensive subjects manifest diastolic dysfunction of the left ventricle in its early hypertensive stage. But yet, it is not clear which paramenter is most sensitive and/or specific, and consistent with pathophysiologic states. In order to have an insight into the problems, 30 hypertensives and 30 normotensive subjects were studied by phonocardiogram and pulsed Doppler echocardiogram at the left ventricular inflow and then isovolumic relaxation time(A2D time), early diastolic deceleration time(EDDT), early diastolic deceleration rate(EDDR), late diastolic time(LDT), E.A velocity ratio[E/A(v)]and E/A area ratioA(a)] were measured and calculated. And the values of each parameters of different groups were subgrouped according to the severity of the hypertension(Group A:mild, B:moderate and C:severe hypertension) and according to the LV mass(Group D:LVMI or =125g/m2) were compared with those of the normal control subjects and also between each subgroups. The results were as follows : 1) In the 30 normotensive subjects, A2D time was averaged out 60.8+/-12.5msec, E/A(v) 1.55+/-0.59, E/A(a) 2.61+/-1.35, EDDT 1.35+/-37.8msec, EDDR8.3+/-4, 6m/sec2 and LDT 151+/-42.2msec. 2) In group A, A2D time was significantly prolonoged(82.5+/-26.0msec, pD and EDDT were significantly prolonged(p<0.005), while E/A(v), E/A(a) and EDDR wer significantly decreased(p<0.005, p<0.05 respectively). 6) In group E, A2D and EDDT were significantly increased(p<0.005, p<0.05 respectively), while E/A(v) and EDDR significantly decreased(p<0.005, p<0.05 respectively). Above results suggest that diastolic function of the left ventricle can be deteriorated in the hypertensive subjects before systolic dysfunction is apparent even in the mild hypertensives and in the patients devoid of hypertensive hypertrophy of the left ventricle.

The Difference of the Rate of Regression of the left Ventricular Mass between the Age Groups in the Hypertensive Patients with the Left Ventricular Hypertrophy with the Control of Blood Pressure by Angiotensin Converting Enzyme Inhibitor

The left ventricular hypertrophy(LVH) in the hypertensive patients is known to be associated with relatively higher risk for cardiovascular morbidity and mortality. In this sense the reversal of LVH with blood pressure control, if attained, could yeild an additional benefit of reducing cardiovascular morbidity and/or mortaility associated with hypertension. However pathogenesis of LVH, the attitude of the LVH to regerss with blood pressure control in a particular patient and whether the regression is really beneficial are not clear. In order to see the effect of angiotensin converting enzyme(ACE) inhibitors on LVH and the age group difference of the LVH regresion, if attainable, 26 hypertensive patients with LVH(LVMI:Left Ventricular Mass Index>125g/m2) were treated with enalapril or captopril for more than 12 weeks and the LVMI followed and the regression rates in younger group "A"(less than 50 years of age) and elder group "B" were compared(LVMI, level of blood pressure, kinds and dosage of enalapril or captopril were not different between the two groups). The LVMI was significantly decreased in both groups, in group A from 191.6+/-74.9g/m2 to 139.7+/-52.0g/m2, and in group B from 185.5+/-58.7g/m2 to 163.9+/-58.7g/m2. In group A the percent decrease of LVMI was significantly higher than that of group B(25.3+/-14.9% versus 10.3+/-8.6%, p<0.005). Above results suggest that enalapril and captopril are equally effective in reducing LVMI in hypertensive patients with LVH and the regression of the LVMI is more marked in the younger age group in this relatively short-term treated small population study.

A Study for the Left Ventricular Diastolic Function in Mild to Moderate Hypertensive Patients without Left Ventricular Hypertrophy

For the evaluation of the left ventricular diastolic function in mild to moderate hypertensive patients without left ventricular hypertrophy, 15 hypertensive patients (group A) and 15 normotensive subjects (group B) were examined by 2-D guided M-mode echocardiography. Various systolic and diastolic indices were derived from computer-assissted analysis of differential curves of left ventricular dimension and posterior wall thickness. The systolic and diastolic function indices of each of the two groups were compared. The results were as follows : 1) There were no significant differences in ejection fraction, left ventricular peak ejection rate and posterior wall thickening rate between two groups. 2) There were no significant differences in % ventricular A wave, left ventricular peak filling rate and posterior wall peak relaxation rate between two groups. 3) One third filling rate was 2.07+/-0.41 EDD/sec in group A and which was significantly lower than 3.29+/-0.88 EDD/sec of group B. Above result suggests that computer-assisted analysis of differential curves of left ventricular dimension and posterior wall thickness could be helpful in the early detection of diastolic dysfunction, and that left ventricular diastolic dysfunction in its early filling period may develop in the mild to moderate hypertensive patients even before left ventricular hypertrophy develops.

A Clinical Study on the Antihypertensive Effects of Enalapril

A new angiotensin converting enzyme inhibitor, enalapril, was administered in 20 hypertensive patients (7 mild, 6 moderate and 7 severe hypertensives) for 8 weeks or longer in order to see the blood pressure lowering effects. Additionally the left ventricular mass index was measured by 2-D guided M-mode echocardiography before and after enalapril therapy, and subjective symptoms and laboratory findings were also followed. The results were as follows: 1) After 8 weeks of enalapril treatment (the doses form 10 mg to 20mg once a day) blood pressure were lowered markedly in 10, moderately in 4, mildly in 4 cases, but the blood pressures were not lowered in 2 cases with severe hypertension. The means of the blood pressures of the group were lowered form 182.1+/-19.2 to 148.0+/-26.0mmHg in systolic and from 111.9+/-14.7 to 95.1+/-17.1mmHg in diastolic after 8 weeks of treatment (p<0.001). 2) Heart rates were not changed significantly with enalapril. 3) The symptoms of insomnia and headache were reported to be improved after enalapril in 13 cases. 4) No discernable changes in CBC and serum level of creatinine were observed. But the random urine protein was decreased in 6 cases with proteinuria in routine urinalysis. The serum lipid profile was not significantly changed, but in the 2 cases in which the ratio of total to HDL-cholesterol was above 5.0, the ratio fell to below 5.0. 5) There was no significant EKG change after enalapril. 6) In 9 cases out of 13 cases with the left ventricular mass index (LVMI) above 125g/m2 BSA, LVMI was followed by echocardiography after enalapril. LVMI was significantly decreased in 8 of 9 cases and mean values after enalapril was decreased from 183.1+/-88.0g/m2 BSA to 150.8+/-61.3g/m2 BSA (p<0.0025). 7) Side effects after enalapril administration were transient dizziness in 4 cases and ageusia in 2 cases. Above results suggest that the enalapril could be an initial choice in the treatment of essential hypertension as a single oral agent in once a day regimen resulting in good antihypertensive effects, improvement of subjective symptoms, regreassion of the left ventricular hypertrophy and few side effects.