Demonstration of diastolic and presystolic Purkinje potentials as critical potentials in a macroreentry circuit of verapamil-sensitive idiopathic left ventricular tachycardia.

OBJECTIVES: The purpose of this study was to determine the relation of diastolic and presystolic potentials recorded during verapamil-sensitive idiopathic left ventricular tachycardia (ILVT) to reentry circuit. BACKGROUND: Successful ablation of verapamil-sensitive ILVT at the zone of slow conduction from which the diastolic potential is recorded has been reported. However, the relationship between the diastolic potential and the reentrant circuit remains a matter of debate. METHODS: Radiofrequency (RF) ablation was performed in 20 patients with verapamil-sensitive ILVT. After identifying the ventricular tachycardia (VT) exit site, we searched for the mid-diastolic potential (P1) during VT. Entrainment followed by RF current application was performed. If the mid-diastolic potential could not be detected, RF current was applied at the VT exit site showing the earliest ventricular activation with a single fused presystolic Purkinje potential (P2). RESULTS: In 15 of 20 patients, both P1 and P2 were recorded during VT from midseptal region. Entrainment pacing captured P1 orthodromically and reset the VT. The interval from stimulus to P1 was prolonged as the pacing rate was increased. Radiofrequency ablation was successfully performed at this site in all 15 patients. After successful ablation, P1 appeared after the QRS complex during sinus rhythm with the identical sequence to that during VT. In the remaining five patients, the diastolic potential could not be detected, and a single fused P2 was recorded only at the VT exit site. Successful ablation was performed at this site in all five patients. CONCLUSIONS: This study demonstrates that P1 and P2 are critical potentials in a circuit of verapamil-sensitive ILVT and suggests the presence of a macroreentry circuit involving the normal Purkinje system and the abnormal Purkinje tissue with decremental property and verapamil-sensitivity.

Prognostic significance of sustained monomorphic ventricular tachycardia induced by programmed ventricular stimulation using up to triple extrastimuli in survivors of acute myocardial infarction.

The prognostic significance of sustained monomorphic ventricular tachycardia (VT) induced by programmed ventricular stimulation using up to 3 extrastimuli was evaluated in 133 consecutive survivors of acute myocardial infarction (AMI) at a mean interval of 1.8 +/- 1.1 months after onset. This was compared with hemodynamic and angiographic abnormalities shown by cardiac catheterization and ventricular ectopic activity detected by Holter monitoring. Sustained monomorphic VT was induced in 25 (19%) patients, sustained polymorphic VT in 11 (8%) patients, nonsustained monomorphic VT (greater than or equal to 10 beats) in 12 patients (9%) and nonsustained polymorphic VT in 9 patients (7%). Multivariate logistic regression analysis of clinical, angiographic, hemodynamic and electrocardiographic variables showed that the presence of a left ventricular aneurysm (p = 0.005) and Lown grade 4B ventricular ectopic activity (p less than 0.001) were independent predictors of inducibility of sustained monomorphic VT. During a mean follow-up of 21 +/- 13 months, there were 8 (6%) sudden cardiac deaths and 3 (2.3%) spontaneous occurrences of life-threatening sustained VT. The 2-year probability of freedom from sudden cardiac death or sustained ventricular tachyarrhythmias was 53 +/- 13% for patients with inducible sustained monomorphic VT, 70 +/- 10% for those with a left ventricular ejection fraction less than 40% and 58 +/- 13% for those with Lown grade 4B ventricular ectopic activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Usefulness of early versus late programmed ventricular stimulation in acute myocardial infarction.

To determine the influence of timing on the prognostic value of programmed ventricular stimulation after acute myocardial infarction (AMI), 32 patients were studied on day 19 (early study) and again on day 36 (late study) after AMI using up to 3 extrastimuli. At the early study, sustained monomorphic ventricular tachycardia (VT) was induced in 12 patients (38%), sustained polymorphic VT in 8 (25%), nonsustained monomorphic VT in 1 (3%), nonsustained polymorphic VT in 1 (3%) and no inducible arrhythmia in 10 (31%). At the late study, sustained monomorphic VT, nonsustained monomorphic VT and nonsustained polymorphic VT were induced in 8 patients (25%) each, and no inducible arrhythmia in 8 (25%). Of the 12 patients who had inducible sustained monomorphic VT at the early study, 7 had noninducibility of sustained monomorphic VT at the late study. Of the 20 patients who had noninducibility of sustained monomorphic VT at the early study, 3 had inducible sustained monomorphic VT at the late study. During the follow-up period (mean +/- standard deviation 21 +/- 8 months), there were 2 sudden cardiac deaths and 3 occurrences of sustained VT. Univariate analysis revealed both inducibilities of sustained monomorphic VT at the early study (p = 0.045) and at the late study (p less than 0.001) to be predictive of sudden cardiac death or clinical occurrence of sustained VT. However, inducibility of sustained monomorphic VT at the late study had a higher sensitivity (100%), specificity (89%), positive predictive value (63%) and negative predictive value (100%) than at the early study (80, 70, 33 and 95%, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical evaluation of urapidil, a new antihypertensive drug: preliminary findings in Japan.

The pharmacokinetics, hypotensive effects, and safety of urapidil were investigated in 22 patients with essential hypertension at four coordinated centers in Japan. The drug was administered in sustained-release capsules given twice daily. The peak plasma concentration of the drug (measured in six patients) was observed four to six hours after administration, and 60% to 70% of the peak concentration was detectable at eight hours. These findings suggest that blood pressure might be controlled by twice-daily administration of urapidil. In 14 outpatients, who received 40 to 80 mg/day of urapidil, systolic and mean blood pressure decreased significantly (P less than 0.05) by week 4, and systolic, diastolic, and mean blood pressure decreased significantly (P less than 0.001) by week 6. In four inpatients, treated with 60 to 120 mg/day of the drug for two weeks, there were significant decreases (P less than 0.05) in systolic, diastolic, and mean blood pressure at day 6 and significant decreases (P less than 0.01) in diastolic and mean blood pressure at day 13. Although side effects were noted in five (23%) of the 22 patients, they were transient and slight in three; in two patients, the side effects disappeared after use of the medication was discontinued. Because the study was carried out in a small number of patients who received different dosages of urapidil over a short period of time, the optimal dosage was not established.

Time-domain and spectral turbulence analyses of the signal-averaged electrocardiogram have different predictive values for sustained ventricular tachycardia in patients with myocardial infarction.

We performed signal-averaged ECG and programmed stimulation in 15 patients after myocardial infarction with ventricular tachycardia and 49 patients after myocardial infarction without ventricular tachycardia to compare the spectral turbulence analysis and time-domain analysis of signal-averaged ECG for prediction of clinical and induced ventricular tachycardia. Sustained monomorphic ventricular tachycardia was inducible in all 15 patients with clinical sustained monomorphic ventricular tachycardia (group 1) and in 9 patients without clinical sustained monomorphic ventricular tachycardia (group 2). Sustained monomorphic ventricular tachycardia was not inducible in 40 patients without clinical sustained monomorphic ventricular tachycardia (group 3). While there was no difference in time-domain variables between groups 1 and 2, there were significant differences between groups 2 and 3. Values obtained by spectral turbulence analysis differed significantly between groups 1 and 2, but not between groups 2 and 3. Time-domain analysis showed abnormal values in 87% of group 1 patients, 78% of group 2, and 35% of group 3. Spectral turbulence analysis showed abnormal values in 93% of group 1, 11% of group 2, and 30% of group 3. In conclusion, frequency-domain spectral turbulence analysis of signal-averaged ECG is more useful than the time-domain analysis in predicting the spontaneous occurrence of sustained monomorphic ventricular tachycardia in patients after myocardial infarction.

[Successfully treated intraoperative coronary artery spasm in a patient with type B dissecting aortic aneurysm: a case report].

A 65-year-old man with chronic type B dissecting aortic aneurysm, complicated by variant from of angina pectoris without any coronary artery obstructed disease on preoperative angiogram was operated upon through left posterolateral thoracotomy under the left heart bypass with Bio-pump system using preoperative Ca antagonists and intraoperative nitroglycerin infusion. Shortly before the end of operation the patient suddenly developed shock status definitely due to coronary artery spasm, associated with ST-elevation in II, III, aVF and bradycardia, then ventricular tachycardia, finally cardiac arrest. The patient was resuscitated by cardiac massage and administration of nifedipine and nitroglycerin. Such attacks repeated five times at ten or twenty minutes intervals. The coronary artery spasm could be successfully suppressed with the additive use of noradrenaline infusion. The patient had no attacks at all postoperatively and was discharged with good success. This case suggests that the prevention of intraoperative coronary artery spasm is essential, but if it occurs, additive use of noradrenaline infusion is effective for the cessation of coronary artery spasm.

[A case of Romano-Ward syndrome effectively treated by propranolol and atrial pacing].

A case of Romano-Ward syndrome effectively treated by both propranolol and atrial pacing is reported. A 33 year-old female, who had experienced syncopal episodes since she was 20 years old, had a family history showing her son with QTc 0.46. Her QT-U interval and QTc were both 0.6 second when propranolol was not administered. It shortened to 0.28 second and 0.39 respectively under exercise stress testing, and also shortened to 0.41 second and 0.43 respectively when left satellite ganglion block was used. Electrophysiologic study demonstrated that both sinus and atrioventricular nodal functions were normal, but the refractory periods of right and left ventricle differed significantly, and nonsustained ventricular tachycardia was induced. Her QT-U and QTc intervals shortened to 0.37 seconds and 0.43 respectively through both the treatment of 80 bpm atrial pacing, and the administration of 80mg propranolol. She has never experienced a syncopal episode.

Hemodynamic studies of nitroglycerin in dogs using an open loop method.

Nitroglycerin is considered to decrease both preload and afterload. To elucidate the actions of nitroglycerin on afterload, venous return was kept constant in this experiment. Three different doses of nitroglycerin, 0.3 microgram/kg/min, 1.0 microgram/kg/min, 3.0 micrograms/kg/min were administered into the ascending aorta of 6 mongrel dogs weighing over 20 kg. These doses of nitroglycerin were randomized in each of six procedures. The plasma concentration of nitroglycerin increased during 10 min of infusion, then it decreased exponentially. Heart rate, cardiac output and left atrial pressure did not change significantly at any dose of nitroglycerin. Systolic blood pressure and systemic vascular resistance (as indices of afterload) decreased significantly during nitroglycerin infusion, especially with the 3 micrograms/kg/min dose. These data suggest that nitroglycerin decreases the afterload. The effects appeared rapidly with administration and disappeared rapidly after cessation of the infusion.

A case of catheter ablation of accessory atrioventricular connection between the right atrial appendage and right ventricle guided by a three-dimensional electroanatomic mapping system.

A 12-year-old girl was referred to our institution because of frequent episodes of AV reciprocating tachycardia. Ventriculoatrial and AV intervals were relatively long along the tricuspid annulus. Earliest retrograde atrial activation was recorded at the mid-portion of the right atrial appendage, 7 mm from the tricuspid annulus. The CARTO electroanatomic mapping system was very useful for providing accurate spatial orientation of the accessory connection. Complete ablation of this connection required multiple radiofrequency energy applications over an extensive area because of the multicomponent structure of the connection.

Comparison of susceptibility of myopotential inhibition between AAI and VVI pacemakers.

Susceptibility of unipolar AAI pacemakers to myopotential inhibition (MPI) was assessed in 10 patients by provocative maneuvers and 24-hour Holter monitoring, and compared to that of unipolar VVI pacemakers in 12 patients. Five maneuvers were performed for each of four different sensitivity levels, and an MPI score of from 0-4 points was given according to the lowest sensitivity level at which MPI was provoked. The MPI score in patients with AAI pacemakers was significantly lower than that in patients with VVI pacemakers, 1.60 +/- 1.26 vs 2.83 +/- 1.03 (p less than 0.05). On Holter monitoring, no MPI was detected in any of the patients with AAI pacemakers, whereas myopotential inhibition was detected in 5/12 patients (42%) with VVI pacemakers. Intracardiac electrograms were of lower amplitudes for AAI pacing than for VVI pacing, 3.13 +/- 1.83 mV vs 11.20 +/- 5.95 mV (p less than 0.01). Although the amplitude of atrial signals was lower than that of ventricular signals, the AAI pacemakers were less susceptible to MPI than were the VVI pacemakers. However, when MPI occurs in AAI pacing, it may be more difficult to correct without undersensing because of the lower amplitude of the intracardiac signals.

Should this patient be paced? An indication for His bundle study: syncope, a normal P-R interval and a narrow QRS.

This report describes a patient who presented with transient central nervous system symptoms of unknown etiology with an electro-cardiogram exhibiting a narrow QRS complex and normal. P-R interval. The decision to implant a permanent VII pacemaker was made on the basis of a His bundle study that revealed significant prolongation of the HV interval. The successful clinical outcome re-emphasizes the clinical usefulness of electrophysiological investigation in patients with syncope of undetermined etiology.

Macroreentry as a mechanism of atrial-induced ventricular ectopic beats: a laboratory curiosity?

During electrophysiologic study in a patient, programmed stimulation of the atrium induced fixed coupled ventricular premature beats on the basis of intraventricular macroreentry. This type of macroreentry, which was reproducible, appears to have been merely a "laboratory curiosity" and never played a clinical role in this patient with chronic recurrent ventricular tachycardia.

A permanently implanted endocardial electrode complicating ventricular tachycardia with a second VT.

A VVI pacemaker was permanently implanted for the purpose of suppressing recurrent ventricular tachycardia (VT). Not only did the device fail to suppress the VT, but also the permanent endocardial electrode caused a second VT which was more rapid and clinically more severe. When a new VT occurs in the presence of a permanently implanted ventricular pacing system, the implanted electrode should be considered as one of the possible etiologic causes for the VT.

Intrahisian functional bundle branch block.

A patient with functional complete left bundle branch block is presented. The site of block was localized to the area of the His bundle. This case demonstrates that functional complete left bundle branch block may be due to longitudinal dissociation in the His bundle.

Catheter ablation of atrioventricular accessory pathway with decremental properties connecting to the tricuspid annulus.

A 65-year-old male with Wolff-Parkinson-White syndrome presented with atrial fibrillation. The patient was found at the electrophysiological study to have two accessory pathways, a Kent fiber and an atrioventricular accessory pathway with decremental properties. The latter pathway conducted exclusively in the antegrade conduction and the ventricular insertion site was the tricuspid annulus. Both accessory pathways were successfully abolished by radiofrequency catheter ablations at the tricuspid annulus. We propose that an atrioventricular accessory pathway with decremental conduction may have various forms concerning not only sites of origin, but also sites of insertion.

Cardiac syncope: a case exhibiting dichotomy between clinical impression and electrophysiologic evaluation.

This case report illustrates the value of electrophysiologic study in patients presenting with graphically unmonitored syncope and/or sudden cardiac death, and who have clinical markers of both bradycardia and ventricular tachycardia. In our patient, a wide QRS on the electrocardiogram and Holter monitor documented high grade ventricular ectopic activity. In this case, had therapy been solely guided by the clinical impression that the patient had ventricular tachycardia, the treatment would have resulted in increasing the risk of recurrence of syncope and/or sudden cardiac death.

Definition of mixing rate of indicator by indicator dilution method: evaluation of relationship between mixing rate of indicator and cardiac output determination.

It is generally agreed that complete mixing of the indicator is one of the most important factors of the indicator dilution method, however, no clear definition of the mixing state has been established. We established a formula for the mixing rate of the indicator by the indicator dilution method, using the concept of entropy in the information theory, and compared the mixing rate of indocyanine green in one mixing chamber (left ventricle) with that in the two mixing chamber system (including the aortic system). The mixing rate of the indicator (M) is shown as M(%) = 100 H/Hcm = -100 (lk sigma ni = 1 Ci + log Ci + log k) (l & k: correction factors in each dye dilution curve, C: mean concentration of the indicator in the region). Left heart and aortic catheterizations by retrograde femoral and carotid artery approach were performed in five anesthetized dogs. Simultaneous dye dilution curves were recorded at the aortic root and at the bifurcation of the abdominal aorta, following the injection of indocyanine green (2.5 mg/1 ml of indocyanine green for each injection) by impulse into the left ventricle at the endsystole, triggered on the R wave of ECG, using the automatic injector devised by the authors. Twenty-five pairs of dye dilution curves were obtained by simultaneous recording in the aortic root and the abdominal aorta under several hemodynamic conditions, and the cardiac output, mean circulation time and the mixing rate of the indicator were determined.(ABSTRACT TRUNCATED AT 250 WORDS)

Novel form of atrial tachycardia originating at the atrioventricular annulus.

We report two patients with reentrant atrial tachycardia that originated at the AV annulus. Atrial tachycardia originated in the posterior portion of mitral annulus in one patient (case 1) and the posterolateral portion of tricuspid annulus in one patient (case 2). Tachycardia was successfully eliminated by RF catheter ablation in both patients, with the catheter placed underneath the mitral valve in case 1 and on the tricuspid annulus in case 2. Spiky potentials were recorded in the diastolic phase of the atrium during tachycardia at the sites of successful ablation. Spiky potentials were also recorded after atrial electrogram during sinus rhythm, and showed decremental properties during atrial pacing. An accelerated atrial rhythm was observed during RF application, and tachycardia could not be induced after ablation in either patient. Tachycardia in these patients seemed to be due to reentrant tachycardia originating in the accessory AV node (Mahaim fiber) without ventricular connection.