High-Resolution Free-Breathing Automated Quantitative Myocardial Perfusion by Cardiovascular Magnetic Resonance for the Detection of Functionally Significant Coronary Artery Disease

AIMS

Current assessment of myocardial ischaemia from stress perfusion cardiovascular magnetic resonance (SP-CMR) largely relies on visual interpretation. This study investigated the use of high-resolution free-breathing SP-CMR with automated quantitative mapping in the diagnosis of coronary artery disease (CAD). Diagnostic performance was evaluated against invasive coronary angiography (ICA) with fractional flow reserve (FFR) measurement.

METHODS & RESULTS

Seven-hundred and three patients were recruited for SP-CMR using the research sequence at 3 Tesla. Of those receiving ICA within 6 months, 80 patients either had FFR measurement, or identification of a chronic total occlusion (CTO) with inducible perfusion defects seen on SP-CMR. Myocardial blood flow (MBF) maps were automatically generated in-line on the scanner following image acquisition at hyperaemic stress and rest, allowing myocardial perfusion reserve (MPR) calculation. 75 coronary vessels assessed by FFR, and 28 vessels with CTO were evaluated at both segmental and coronary territory level. Coronary territory stress MBF and MPR were reduced in FFR-positive (≤ 0.80) regions (median stress MBF: 1.74 [0.90-2.17] ml/min/g; MPR: 1.67 [1.10-1.89]) compared with FFR-negative regions (stress MBF: 2.50 [2.15-2.95] ml/min/g; MPR 2.35 [2.06-2.54] p < 0.001 for both). Stress MBF ≤ 1.94 ml/min/g and MPR ≤ 1.97 accurately detected FFR-positive CAD on a per-vessel basis (area under the curve: 0.85 and 0.96 respectively; p < 0.001 for both).

CONCLUSIONS

A novel scanner-integrated high-resolution free-breathing SP-CMR sequence with automated in-line perfusion mapping is presented which accurately detects functionally significant CAD.

[Value and safety of ambulatory electrophysiologic study]

One-hundred-thirty patients underwent 53 electrophysiological studies including programmed atrial and ventricular stimulation and 96 atrial overdrive stimulations on an outpatient basis. The indications for electrophysiological study were disabling palpitation, syncope, or presyncope, intracardiac conduction disturbance, and bradyarrhythmia. In one patient the efficacy of oral antiarrhythmic drug therapy was evaluated by repeat electrophysiological study. Atrial overdrive stimulation was performed in patients with atrial flutter or atrial tachycardia. On the basis of the result of electrophysiological testing, 25 patients were believed not to require any treatment, 16 patients received new drug therapy, 7 patients underwent catheter ablation in a second session, 2 patients had either a pacemaker or an ICD implanted, and 1 patient continued to receive the drug therapy that had been tested. Atrial overdrive stimulation resulted in a regular sinus rhythm in 66 patients (69%). Except for one patient in whom atrial flutter could not be terminated, atrial fibrillation was induced in the remaining 30 patients. After the procedure, patients were monitored for 30 min in case of overdrive stimulation, and for approximately 3 h after electrophysiological study or 6 h if additional coronary angiography had been performed. Severe complications were not observed. In 10 cases minor hematoma occurred at the puncture site without serious sequelae.--Outpatient electrophysiological study as well as atrial overdrive stimulation are feasible and safe in a selected group of patients.

[Ambulatory catheter ablation. Indications, results and risks]

The purpose of this study was to test the efficacy, feasibility, and safety of outpatient radiofrequency catheter ablation in 162 consecutive patients. There were 83 men and 79 women at a mean age of 47 + 15 years; 13 patients underwent 2 and 1 patient 3 ablation procedures. In 167 cases patients suffered from highly symptomatic paroxysmal tachycardia associated with presyncope or syncope in 74. Severe palpitations were present in 7 cases and recurrent syncope in 1 case. One patient had an asymptomatic Wolff-Parkinson-White syndrome with a shortest RR-interval during atrial fibrillation of 150 ms. The mechanism of tachycardia was found to be atrioventricular nodal reentry in 78 cases, atrioventricular reentry involving an accessory atrioventricular pathway in 56, atrial fibrillation in 16, atrial flutter of the common type in 15, ectopic atrial tachycardia in 8, and idiopathic ventricular tachycardia in 3. Catheter ablation was performed in these 176 cases at an overall success rate of 86%. In 148 cases patients could be treated on an outpatient basis and were discharged after a maximal observation time of 3 hours in 28, and 24 hours in another 120 cases. Short-term follow-up was uneventful in these patients. After 28 ablation procedures patients had to be admitted to the hospital, because of pain at the puncture sites or after pacemaker implantation in 15 cases, because of minor complications in 12, and because of pericardial tamponade in 1 case. Another severe complication occurred in 1 patient after successful ablation of right atrial tachycardia. Three days after discharge the patient suffered from pulmonary embolism originating from a thrombus at the ablation site. After hospital admission the patient recovered completely. In general, complication rate was 2.27%. This study shows that catheter ablation can be performed effectively and safety on an outpatient basis.

Recanalization of chronic coronary artery occlusions using laser followed by balloon angioplasty

Excimer laser angioplasty with adjunctive percutaneous transluminal coronary angioplasty of chronic coronary artery occlusions was performed using the Litvack 1.3 Z laser catheter in 80 patients in whom the occlusion could be passed by a guidewire; success rate was 89%. Angiographic follow-up revealed a restenosis rate of 33% and a reocclusion rate of 20%, and clinical follow-up showed a significant symptomatic improvement. It is concluded that laser angioplasty is a promising method for the treatment of chronic coronary artery occlusions.

A new variant of type IV glycogenosis with primary cardiac manifestation and complete branching enzyme deficiency. In vivo detection by heart muscle biopsy

Type IV glycogenosis (polyglucosan body disease) is a rare congenital autosomal recessive inherited disorder, caused by lack of the branching enzyme (amylo-1,4-1,6 transglucosidase). This deficiency leads to storage of abnormal glycogen (polyglucosan bodies) in the liver and other tissues. The clinical onset of the disease is insidious with non-specific gastrointestinal symptoms followed by progressive hepatic failure. Usually patients die due to hepatic cirrhosis within 4 years. Sometimes myopathy of the heart and skeletal muscle is also present. In these cases, the clinical onset is often later than in typical cases. We report on two brothers with primarily cardiac manifestation and late onset of the disease. The older one started to suffer from progressive dilated cardiomyopathy at the age of 18 years, presenting with severe heart failure, hepatosplenomegaly, ascites and peripheral oedema. He also demonstrated myopathy and muscular atrophy especially of the shoulder and lower limbs. Initially he improved on medical therapy, but one year later severe heart failure recurred followed shortly afterwards by sudden cardiac death. Right heart and skeletal muscle biopsies were performed while he was alive. These, as well as the autopsy, revealed massive accumulation of polyglucosan bodies. In both heart and skeletal muscle, complete branching enzyme deficiency could be proven. His 14-year-old brother showed similar clinical findings of mild dilated cardiomyopathy. His muscle biopsy also revealed polyglucosan body myopathy. Thus, in young patients presenting with congestive cardiomyopathy, type IV glycogenosis has to be considered in the differential diagnosis.

Preexcitation in hypertrophic cardiomyopathy: a case of a fasciculoventricular Mahaim fiber

A patient with hypertrophic cardiomyopathy (HCM) who presented with preexcitation pattern on the surface ECG suggestive of the Wolff-Parkinson-White (WPW) syndrome is described. Intracardiac electrophysiological study revealed a fixed anomalous QRS complex and a short-fixed His-ventricular interval indicating a fasciculoventricular Mahaim fiber. As this specific form of accessory connection does not cause reentrant tachycardias, no treatment was required. It is important to distinguish this entity from atriofascicular or nodoventricular Mahaim fibers or the WPW syndrome in patients with HCM showing a preexcitation pattern in the surface ECG, as these may cause life-threatening arrhythmias in this patient population.

[Does rotablation of complex coronary artery stenosis lower the risk of subsequent PTCA?]

To answer the question of whether pretreatment of complex coronary artery lesions via rotablation reduces the risk of subsequent PTCA, we compared the results of PTCA of 250 patients with Typ B- and C-lesions treated between April 1 and November 11 1991 (Group A) with a group of 437 patients treated between January 1 and May 1 1992 (Group B), for whom not only PTCA but also rotablation was available. Rotablation was successful in 102 of 119 procedures (85.7%), the rate of major complications was 1.8%. The primary success rate for treatment of all complex lesions was higher in group B (87.3%) in which 22.2% of the lesions were treated with the rotablator than in group A (83.1%). Dissection rate was similar in both groups (18.5% in group A, 17.5% in group B). In group B patients, however, dissections could be controlled more frequently by the use of a reperfusion catheter (21% vs 8.3% in group A). Serious complications caused by a dissection were not so often observed. In group B patients the rate of major complications due to dissection was lower (2.5% vs 4.4% in group A). In summary, pretreatment of complex coronary artery lesions via rotablation seems to increase the success rate of the following PTCA and to reduce its risks.

[Early hemostasis after coronary therapeutic interventions by using a collagen plug]

Significant bleeding at the puncture site is one of the most important problems in the care of patients undergoing interventional coronary procedures like PTCA, rotablation, laser angioplasty or stent implantation. This is due to systemic application of heparin, acetylic salicic acid and, in stent patients, even additional coumadine. Furthermore, the interventional systems implement catheter systems with a large inner and outer lumen leading to increased vessel trauma. To decrease the risk of bleeding and to reduce the time of pressure dressing and bed rest, a bovine collagen plug (VasoSeal) was used in 600 consecutive patients undergoing one of the above-mentioned interventional procedures. In the majority of patients (pts.) (474/600 = 79%) either no (404 pts.) or minimal (70 pts.) bleeding occurred. Bed rest could be reduced from more than 24 h to 6-12 h. In 65/600 pts. (11%) significant bleeding developed which could be controlled by compression. Bed rest in these patients was 13-20 h. Larger bleedings or complications occurred in 61/600 pts. (10.2%) and could be controlled conservatively in all but eight patients. One patient (0.2%) had a narrowing of the artery at the puncture site after the procedure, probably due to intraarterial plug application. In another patient (0.2%) embolization of the plug into the popliteal artery occurred which could be treated by embolectomy using a Fogarty-catheter. Arteriovenous fistulae or aneurysms developed in 8/600 pts. (1.3%) but these are no specific complications of the hemostatic device. The plug could not be placed in 13/600 pts. (2%), mainly in the beginning of the study.(ABSTRACT TRUNCATED AT 250 WORDS)

[Successful high-frequency catheter ablation of an accessory atrioventricular conduction pathway in atrial fibrillation]

This report describes the case of a 41-year-old patient with Wolff-Parkinson-White syndrome and recurrent, highly symptomatic episodes of atrial fibrillation (with rapid heart rates of a mean of 250 beats/min) in whom transvenous catheter ablation of the accessory pathway was successfully performed in a relatively short time during the arrhythmia. The feasibility of an abbreviated approach to the relatively time-consuming ablation procedure in Wolff-Parkinson-White syndrome is discussed.

Intravenous dantrolene does not exhibit calcium channel blocking effects on the cardiac conduction system in humans

In malignant hyperthermia, dantrolene, a drug assumed to possess calcium channel blocking properties, effectively suppresses supraventricular and ventricular arrhythmias. To investigate antiarrhythmic properties of dantrolene, six patients (three women and three men, age 42 +/- 18 yr) with symptomatic atrioventricular (AV)-nodal reentry tachycardia were studied. Electrocardiographic measurements included sinus cycle length, PQ-interval, width of the QRS-complex, and QT- and rate-corrected QT-interval. During the electrophysiologic study, effective refractory periods of the right atrium, AV node, right ventricle, and AV-nodal conduction intervals were determined, and AV-nodal reentry tachycardia was induced in all patients. Dantrolene was administered intravenously over a period of 15 min at doses of 1.0, 1.5, or 3.0 mg/kg in two patients each. The dosage was not further increased because of side effects at the dose of 3.0 mg/kg. After the infusion of dantrolene, the electrocardiographic measurements and electrophysiologic study were repeated. The plasma concentrations of dantrolene ranged from 1.69 to 6.61 micrograms/ml at the time of the electrophysiologic study. After dantrolene administration, the sinus cycle length shortened from 686 +/- 80 to 622 +/- 55 ms (P less than 0.05). No significant changes of any other parameter could be demonstrated after intravenous dantrolene. AV-nodal reentry tachycardia remained inducible in all patients without change of the tachycardia cycle length and without change in coupling intervals of tachycardia-inducing extrastimuli. Antiarrhythmic properties of dantrolene could not be demonstrated in patients with AV-nodal reentry tachycardia at therapeutic doses.(ABSTRACT TRUNCATED AT 250 WORDS)

[A iatrogenic arteriovenous fistula following laminectomy. A rare differential diagnosis of heart failure]

An abdominal murmur was first heard in a now 46-year-old man four years after laminectomy at the age of 21. Signs of right heart failure and, ultimately, of global heart failure developed progressively and increasingly 20 years later. Echocardiography demonstrated enlargement of the right heart cavities, and atrial fibrillation was diagnosed. Cardiac catheterization revealed the typical picture of high output failure (cardiac output 13.9 l/min). Intra-arterial subtraction angiography demonstrated a fistula between the left iliac artery and vein. After operative closure of the fistula the signs of heart failure disappeared. Six months later a residual but insignificant fistula was still present, as well as persistent atrial fibrillation. Medical treatment having failed cardioversion successfully re-established sinus rhythm and the patient became symptom-free. Arteriovenous fistula after laminectomy is a rare cause of heart failure and often diagnosed very late. The prognosis is good once the fistula has been closed.

Sites of conduction block in accessory atrioventricular pathways. Basis for concealed accessory pathways

Catheter recordings of accessory pathway (AP) activation were used to identify the site of antegrade and retrograde AP conduction block in 126 consecutive patients undergoing electrophysiological testing. Activation was recorded from 89 of 121 left free-wall and posteroseptal pathways (left APs) and from 12 of 24 right free-wall, midseptal, and anteroseptal pathways (right APs). The recorded APs were further subdivided into those exhibiting consistent antegrade conduction during sinus rhythm (overt APs: 50 left APs, eight right APs), those exhibiting intermittent antegrade conduction (intermittent APs: six left APs, two right APs), and those exhibiting only retrograde conduction (concealed APs: 33 left APs, two right APs). The sites of block were recorded during decremental atrial and ventricular stimulation. The sites of both antegrade and retrograde block were determined in 40 of 50 overt left APs and six of eight overt right APs. Antegrade and retrograde block occurred at or near the AP-ventricular (AP-V) interface in 37 of 40 overt left APs and two of six overt right APs and at the atrial-AP (A-AP) interface in one of 40 overt left APs and four of six overt right APs. In three of three overt left APs with no retrograde conduction, retrograde block occurred at or near the AP-V interface. The site of antegrade and retrograde block differed in only two of 58 overt pathways. There was no difference between overt APs limited at the A-AP or the AP-V interface in the shortest atrial or ventricular pacing cycle length maintaining 1:1 antegrade or retrograde AP conduction, respectively. Both antegrade and retrograde block occurred near the AP-V interface in four of six intermittent left APs and zero of two intermittent right APs and near the A-AP interface in two of six intermittent left APs and one of two intermittent right APs. The sites of both antegrade and retrograde block were determined in 28 of 33 concealed left APs, and both occurred at or near the AP-V interface in 26 and A-AP interface in two APs. In two of two concealed right APs, antegrade block occurred at the AP-V interface. These findings suggest that both antegrade and retrograde conduction are limited by factors operating near the AP-V interface in overt left APs and at the A-AP or AP-V interface in overt right APs. Factors limiting antegrade conduction in concealed APs appear to be located almost always near the AP-V interface.

Ablation of a left-sided free-wall accessory pathway by percutaneous catheter application of radiofrequency current in a patient with the Wolff-Parkinson-White syndrome

A case is presented of a 20-year-old woman with a history of three episodes of syncope within the last 4 years, which was caused by a rapid ventricular response to atrial fibrillation via a left-sided posterior accessory pathway. A variety of antiarrhythmic agents had failed to control the arrhythmia. Using a novel dual catheter approach, with one catheter in the coronary sinus and an adjacent catheter in the left ventricle close to the mitral annulus, accessory pathway conduction was successfully interrupted by two radio-frequency current applications between the tip electrodes of the two catheters. During follow-up, 12-lead electrocardiograms have been normal and the patient has been asymptomatic.

Pleomorphic ventricular tachycardia: demonstration of conduction reversal within the reentry circuit

A case is presented of a patient with incessant ventricular tachycardia of left bundle branch block morphology. Endocardial mapping revealed the site of earliest activation during tachycardia to be the proximal right ventricular septum. Pacing at this site elicited the clinical tachycardia, whereas pacing at the proximal left ventricular septum induced a right bundle branch block morphology identical to that of a previously recorded spontaneous ventricular tachycardia. Electrophysiological evidence is given that both types of tachycardia originate from a single reentry circuit located in the proximal ventricular septum in which the reentrant wavefront may travel either orthodromically (during spontaneous tachycardia and right ventricular pacing) or antidromically (during left ventricular pacing).

Diprafenone for treatment of Wolff-Parkinson-White syndrome

The effect of intravenous (1.5 to 2.0 mg/kg body weight) and oral (300 to 375 mg/d) diprafenone was studied in 15 patients with the Wolff-Parkinson-White syndrome and symptomatic supraventricular tachycardia. Intravenous application of diprafenone significantly increased atrioventricular nodal conduction time as well as the effective refractory periods of the right ventricle and the accessory pathway in both the antegrade and retrograde directions. Antegrade conduction block in the accessory pathway occurred in two patients after the dose was increased to 2.0 mg/kg body weight. Intravenous diprafenone suppressed the inducibility of supraventricular tachycardia in two patients, but the tachycardia cycle length was significantly increased in all other patients. Fourteen patients were treated with oral diprafenone, and 11 were asymptomatic during a 17-month follow-up, two of these after the dose had been increased to 375 mg/d. Oral therapy had to be withdrawn in two patients because of adverse gastrointestinal side effects and in one because of recurring bronchospasm.

Encainide versus flecainide for chronic atrial and junctional ectopic tachycardia

For treatment of chronic atrial and junctional ectopic tachycardia, standard antiarrhythmic therapy has been shown to be ineffective in most patients. Both the intravenous efficacy and the oral efficacy of 2 class IC antiarrhythmic drugs, encainide and flecainide, were studied in 16 patients with atrial ectopic tachycardia and in 3 patients with junctional ectopic tachycardia, using exercise testing, 24-hour long-term electrocardiography and programmed electrical stimulation. All patients had been previously treated unsuccessfully with several antiarrhythmic drugs. In 5 patients, tachycardia was persistent; in the remaining patients, it occurred intermittently for more than 12 hours/day. Intravenous encainide, in doses ranging from 0.3 to 2.0 mg/kg body weight, was given to 5 patients with atrial ectopic tachycardia, and it terminated atrial ectopic tachycardia in all patients. Intravenous flecainide was given to 9 patients, and it terminated atrial tachycardia in 4 and slowed the tachycardia rate in 2. It terminated junctional tachycardia in 2 patients and slowed tachycardia rate in 1. During a follow-up period of 10 +/- 5 months, oral encainide, in dosages between 150 and 225 mg/day, completely suppressed atrial ectopic activity in 4 patients. In the remaining patient, encainide reduced the number of tachycardia episodes markedly but had to be withdrawn because of intolerable side effects. During a 12 +/- 11-month (median 6) follow-up, oral flecainide at dosages between 200 and 300 mg/day, completely suppressed ectopic activity in 7 patients and improved symptoms in 5. Only 1 patient failed to respond to oral flecainide. The results of this study indicate that both encainide and flecainide are effective in the treatment of chronic ectopic atrial and junctional tachycardia.

[Catheter-induced modulation of the electric conductivity of the atrioventricular node by high-frequency current]

A radio-frequency current was delivered via a catheter to the atrioventricular (AV) node in 13 patients with supraventricular arrhythmias (maximal heart rate 215/min). In nine patients with atrial fibrillation, three with AV nodal re-entry tachycardia and one with AV re-entry tachycardia, AV node conduction time was prolonged from 95 +/- 43 ms to 168 +/- 72 ms. In three patients the radio-frequency current had no lasting effect, necessitating AV node ablation with a direct-current shock. During a mean observation period of five months, all ten patients in whom the radio-frequency current had been successfully applied remained free of symptoms without any anti-arrhythmia treatment. There were no complications during or after treatment.

[Electrophysiologic properties of accessory atrioventricular pathways. Comparison with myocardial tissue and relation to site]

In 45 patients (15 female, 30 male; age 34 +/- 12 years) with Wolff-Parkinson-White syndrome: 1) the relation between electrophysiologic properties and location of accessory pathways and 2) the relationship between electrophysiologic properties of accessory pathways and adjacent atrial and ventricular myocardium was studied. Location of the accessory pathways was determined by catheter mapping of the coronary sinus and the tricuspid valve ring. There was no linear correlation between antegrade and retrograde effective refractory periods of accessory pathways and adjacent myocardial tissue. According to their location, accessory pathways were divided into right lateral (n = 4), anteroseptal (n = 6), posteroseptal (n = 10), left posterolateral (n = 8), and left lateral (n = 17). While analysis of variance revealed no differences between subgroups concerning retrograde effective refractory periods, antegrade effective refractory periods were significantly different (p less than .01). Moving in a clockwise direction around the mitral valve ring, antegrade effective refractory periods of the accessory pathways decrease from anteroseptal (321 +/- 30 ms) to posteroseptal (290 +/- 38 ms), left posterolateral (258 +/- 21 ms) and left lateral (246 +/- 27 ms), (Spearman R = 0.70m, p less than .01). Antegrade effective refractory periods of septally located accessory pathways (301 +/- 38) were significantly longer than of pathways located in the free wall of the ventricles (251 +/- 24, p less than .01).

Modification of a left-sided accessory atrioventricular pathway by radiofrequency current using a bipolar epicardial-endocardial electrode configuration

Transcatheter ablation of a left posterolateral free wall accessory atrioventricular pathway using radiofrequency current and a bipolar epicardial-endocardial electrode configuration was attempted in a 19-year-old woman. The patient had suffered from recurrent syncope due to atrial fibrillation with rapid conduction to the ventricles. Following applications of radiofrequency current between one electrode in the coronary sinus and another in the left ventricle placed high against the mitral annulus, the anterograde effective refractory period was increased from less than 205 ms to a lasting value of 460 ms. Radiofrequency application could be performed without general anaesthesia and caused no side-effects.

Percutaneous catheter ablation at the mitral annulus in canines using a bipolar epicardial-endocardial electrode configuration

For potential application in ablating left free-wall accessory AV pathways with direct current shocks, a new epicardial-endocardial electrode configuration, designed to focus the current field across the mitral annulus, was tested in dogs. A catheter electrode in the coronary sinus (epicardial electrode) was used as the cathode, and a catheter electrode in the left ventricle (endocardial electrode) placed beneath the mitral valve, high against the mitral annulus and directly across from the epicardial electrode formed the anode. Two shocks, each of 30, 40, or 50 joules (J) were delivered in nine, three, and four dogs, respectively. The first shock was applied to the anterior or lateral wall and the second shock to the posterior wall, except in one dog which received one anterior and one lateral shock. Two dogs receiving 50 J shocks died acutely, one due to rupture of the coronary sinus and cardiac tamponade and the other had unexplained electromechanical dissociation. The remaining 14 dogs tolerated the two shocks well and were sacrificed 3-5 days later for pathological examination of the heart. Shocks in the anterior and lateral regions produced atrial necrosis (height 1.5-11 mm, width 1.5-12 mm and depth 1-3 mm) in 10 of 14 dogs and ventricular necrosis (height 4-27 mm, width 4-33 mm, and depth 5-14 mm) in all 14 dogs. Ideal lesions with atrial necrosis extending down to the annulus and ventricular necrosis extending to the epicardial aspect of the ventricular crest occurred in five dogs in which the endocardial electrode was positioned high against the annulus. In the other nine dogs, the endocardial electrode was located 6-18 mm below the annulus, as estimated by the center of ventricular necrosis. In these dogs, the ventricular lesions did not extend to the epicardial aspect of the crest and, in four dogs, no atrial necrosis was found. Shocks delivered to the posterior wall produced no atrial or ventricular necrosis except in one dog receiving a 50 J shock. It is concluded that, using the epicardial-endocardial electrode configuration with the LV catheter positioned high against the annulus, shocks of less than 50 J in dogs safely produce atrial and ventricular necrosis adjacent to the mitral annulus in the anterior and lateral regions but not in the posterior regions. Similar lesions in man may be capable of interrupting left anterior and lateral accessory AV pathways.

Programmed electrical stimulation in hypertrophic cardiomyopathy. Results in patients with and without cardiac arrest or syncope

Programmed electrical stimulation was performed in 54 consecutive patients with hypertrophic cardiomyopathy. There were 11 'symptomatic' patients: three had a history of cardiac arrest due to ventricular tachyarrhythmias (group A), and eight had a history of syncope of unknown origin (group B); 43 patients were 'asymptomatic', i.e. they had no documented or suspected symptomatic ventricular arrhythmias (group C). There were no differences among the groups with respect to electrocardiographic, echocardiographic or hemodynamic data. Ventricular arrhythmias were induced by atrial and right and left ventricular stimulation with a maximum of two extrastimuli in 18 patients. Induced arrhythmias were repetitive ventricular response in six patients, nonsustained ventricular tachycardia in four, sustained ventricular tachycardia in five, and ventricular fibrillation in three patients. With one exception, ventricular tachycardia was always rapid (cycle lengths ranged from 180 to 250 ms); it was polymorphic in six patients and monomorphic in three. Atrial stimulation induced rapid monomorphic ventricular tachycardia in one group A patient. The type and incidence of induced ventricular arrhythmias did not differ among the three groups. It is concluded that programmed electrical stimulation induces the same type of ventricular arrhythmia (rapid polymorphic ventricular tachycardia or ventricular fibrillation) in 'symptomatic' and 'asymptomatic' patients with hypertrophic cardiomyopathy, the incidence in the latter group being 19%. Induction by atrial stimulation of a rapid ventricular tachycardia may be a specific finding to identify patients with hypertrophic cardiomyopathy at risk for exercise-induced ventricular fibrillation.

Train stimulation at the atria for prevention of atrioventricular tachycardia: dependence on accessory pathway location

In 12 patients with accessory pathway-mediated supraventricular tachycardia, programmed electrical stimulation with a rapid train of 10 stimuli was assessed for prevention of tachycardia induction. Tachycardia was induced with one or two extrastimuli from both the right and the left atrium (by way of the coronary sinus). Preventive train stimulation, with the train delivered after the tachycardia-initiating stimulus, was attempted at the site of tachycardia induction as well as at the opposite site. Prevention at the site of tachycardia induction was successful in all patients when the length of the train (90 ms) exceeded the effective refractory period of the tachycardia-initiating stimulus to achieve single atrial capture within the "preventive zone." However, in patients with a left-sided accessory pathway, preventive stimulation at the right atrium failed when tachycardia was induced from the coronary sinus because of interatrial conduction delay. It is concluded that train stimulation is an effective mode for supraventricular tachycardia prevention, yet the site of preventive stimulation should lie as close as possible to the anatomic site of the reentrant circuit to reduce interatrial conduction delay.

Sotalol in patients with Wolff-Parkinson-White syndrome

We evaluated the effects of intravenous and long-term oral sotalol treatment in 17 patients with an accessory atrioventricular (AV) pathway. All patients had a history of symptomatic supraventricular tachycardia. During electrophysiologic study intravenous (1.5 mg/kg body weight) and oral (240 to 320 mg/day) sotalol caused significant increases of sinus cycle length, AV nodal conduction time, and refractory periods of atrial and ventricular myocardium and accessory pathway. AV reciprocating tachycardia, which was inducible and sustained in 15 patients at control, was still inducible after intravenous sotalol in 14 patients, including one in whom it was not inducible at control. However, tachycardia became nonsustained in 10 patients. In seven patients who underwent repeat drug testing while on oral sotalol, results were the same as after intravenous sotalol. Sixteen patients were followed-up for 36 months (median value). Fifteen of them were clinically free of symptoms or experienced marked improvement, despite recurrences of tachycardia in two. In a third patient sotalol had to be withdrawn because of recurrent supraventricular tachycardia. Orthostatic hypotension occurred in five patients and required withdrawal of sotalol in one. To predict the long-term clinical outcome of patients, exercise testing and Holter monitoring were of little or no value. Programmed electrical stimulation predicted clinical outcome in 63% after intravenous and in 86% after oral sotalol. This study shows that long-term treatment with sotalol is highly effective in patients with the Wolff-Parkinson-White syndrome and regular supraventricular tachycardia.

[High-frequency stimulation in the prevention of atrioventricular tachycardias: relation to stimulation site and location of the accessory conduction pathway]

To assess the validity of train stimulation for the prevention of accessory pathway mediated atrioventricular tachycardia, thirteen patients were studied. Tachycardia was induced from high right atrium and coronary sinus by means of single extrastimuli; preventive stimulation at high right atrium and coronary sinus consisted of the delivery of a train of ten or eleven stimuli 10 ms apart, following the tachycardia initiating stimulus. Preventive train stimulation at the site of tachycardia induction was successful in all patients when the train exceeded the atrial effective refractory period of the initiating stimulus to achieve single atrial capture within the "preventive zone". In patients with a left-sided accessory pathway in whom tachycardia was induced from the coronary sinus, preventive stimulation at high right atrium failed because of interatrial conduction delay. It is concluded that train stimulation is an effective mode of prevention of atrioventricular reentrant tachycardia, yet preventive stimulation should be performed as close as possible to the reentry circuit to reduce interatrial conduction delay.

Significance of timing programmed electrical stimulation after acute myocardial infarction

To assess the influence of time on the inducibility by programmed electrical stimulation of ventricular arrhythmias after acute myocardial infarction, 18 patients were studied on day 5 and day 24 after infarction with a stimulation protocol employing a maximum of three right ventricular extrastimuli during sinus rhythm and at three paced cycle lengths. All patients were without documented sustained ventricular arrhythmia (sustained ventricular tachycardia or ventricular fibrillation) before the investigation. Sustained ventricular arrhythmia was induced in two patients on day 5, but in nine on day 24 after infarction. This difference in incidence was statistically significant (p less than 0.05), as was the change in the distribution ratio of induced sustained ventricular arrhythmia from day 5 to day 24 (p less than 0.05). The types of arrhythmia induced on day 24 were sustained ventricular tachycardia with a mean cycle length of 207 ms in six cases (five monomorphic, one polymorphic), and ventricular fibrillation in three cases. These nine patients did not differ from the remaining nine patients in maximal serum creatine kinase, infarct site, number of stenosed coronary arteries, global left ventricular ejection fraction (47 +/- 7% versus 46 +/- 10%) and results of 24 hour ambulatory electrocardiographic (Holter) monitoring, but they had a significantly shorter right ventricular effective refractory period (223 +/- 10 ms versus 259 +/- 28 ms; p less than 0.05). During the follow-up period of 24 +/-5 months no patient died, had syncopal attacks or developed spontaneous episodes of sustained ventricular arrhythmia.(ABSTRACT TRUNCATED AT 250 WORDS)

[Programmed electric stimulation following acute myocardial infarct. Significance of stimulation timing]

To assess the influence of time on the inducibility by programmed electrical stimulation of ventricular arrhythmias after acute myocardial infarction, we studied 18 patients on the 5th and 24th day after infarction with a stimulation protocol employing a maximum of 3 right ventricular extrastimuli during sinus rhythm and at 3 paced cycle lengths. All patients were without documented sustained ventricular arrhythmias (sustained ventricular tachycardia or ventricular fibrillation) prior to the investigation. Sustained ventricular arrhythmias were induced in 2 patients on day 5, but in 9 on day 24 after infarction. This difference in incidence was statistically significant (p less than 0.05), as was the change in the distribution ratio of induced sustained ventricular arrhythmias from day 5 to day 24 (p less than 0.05). The types of arrhythmia induced on day 24 were sustained ventricular tachycardia with a mean cycle length of 207 ms in 6 cases (5 monomorphic, 1 polymorphic), and ventricular fibrillation in 3 cases. These 9 patients did not differ from the remaining 9 patients in maximal CPK, infarct site, number of stenosed coronary arteries, global left ventricular ejection fraction, and in the results of 24-hour Holter monitoring, but they had a significantly shorter right ventricular effective refractory period (223 +/- 10 ms versus 259 +/- 28 ms; p less than 0.05). During the follow-up period of 24 +/- 5 months no patient died, had syncopal attacks, or developed spontaneous episodes of sustained ventricular arrhythmia. The timing of programmed electrical stimulation with a maximum of 3 right ventricular extrastimuli strongly influences the inducibility of sustained ventricular arrhythmias after acute myocardial infarction.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of encainide and flecainide on chronic ectopic atrial tachycardia

In the treatment of chronic ectopic atrial tachycardia, standard antiarrhythmic therapy has been shown to be ineffective in the majority of patients. The intravenous and oral effects of two class IC antiarrhythmic drugs, encainide and flecainide, in five patients with chronic ectopic atrial tachycardia were studied using exercise testing, 24 hour long-term electrocardiography and programmed electrical stimulation. All patients had been treated unsuccessfully with at least four antiarrhythmic drugs. In two patients tachycardia was persistent, and in three patients tachycardia occurred intermittently for more than 12 hours/day. Intravenous encainide and flecainide at doses ranging from 0.3 to 2.0 mg/kg and from 0.5 to 1.5 mg/kg body weight, respectively, terminated atrial ectopic tachycardia in all patients. Oral encainide, 150 to 225 mg/day, completely suppressed ectopic atrial activity in four patients during a mean follow-up period of 8 +/- 3 months. In the remaining patient encainide markedly reduced the number of episodes of tachycardia. In three patients encainide had to be withdrawn because of intolerable side effects. These patients were well controlled with oral flecainide, 200 to 300 mg/day, without side effects. On the basis of these results, the efficacy of encainide and flecainide in the treatment of chronic ectopic atrial tachycardia appears to be not drug-specific but rather a general class IC property.

Right atrial thrombus formation after transvenous catheter ablation of the atrioventricular node

The formation of a right atrial mass was detected in a patient by two-dimensional echocardiography 3 weeks after successful transvenous electrical ablation of the atrioventricular node had been performed. The mass was attached to the atrial septum at the site where the electrode catheter used for the ablation had supposedly been located and it exhibited no mobility. It was interpreted as a right atrial thrombus induced by the ablation procedure. Although no pulmonary embolic events have been observed during a 7 month follow-up period, right atrial thromboembolism must be considered a potentially dangerous complication of transvenous catheter ablation to control cardiac arrhythmias.

Spontaneous termination of reciprocating tachycardia owing to interaction of dual atrioventricular nodal pathways in patients with an accessory pathway

Retrospective analysis of the electrophysiologic recordings from 125 consecutive patients with reciprocating tachycardia involving an accessory atrioventricular (AV) pathway suggested, by the mode of spontaneous termination of reciprocating tachycardia, the coexistence of dual AV nodal pathways in 7 patients. Three different modes of spontaneous tachycardia termination were observed. In 2 patients with antidromic tachycardia, termination was a result of AV nodal reentry, preceded by a decrease in retrograde AV nodal conduction. In 3 other patients with antidromic tachycardia, termination occurred after a sudden switch from a slow to a fast AV nodal pathway, leading to conduction block in either the accessory pathway or the His-Purkinje system. In 2 patients with orthodromic tachycardia, termination was caused by a sudden change of anterograde conduction from a fast to a slow AV nodal pathway, eliciting an AV nodal echo beat. The interaction of dual AV nodal pathways within the reentry circuit incorporating the accessory pathway always inhibited sustained reciprocating tachycardia.

[Right atrial thrombus formation following transvenous catheter ablation of the AV conduction system]

A case is reported in which the formation of a right atrial mass was detected by two-dimensional echocardiography 3 weeks after successful transvenous electrical ablation of the atrioventricular junction had been performed. The mass was attached to the atrial septum at the site where the electrode catheter used for the ablation had been located and it exhibited no mobility. It was interpreted as a right atrial thrombus induced by the ablation procedure. Although no pulmonary embolic events have been observed during a 7-month follow-up period, right atrial thrombus formation must be considered as a potentially dangerous complication of transvenous catheter ablation to control supraventricular arrhythmias.

Prevention of reentrant tachycardia by single beat or repetitive stimulation

Eleven patients with an atrioventricular accessory pathway were studied by programmed electrical stimulation to determine if reentrant tachycardia could be prevented by delivery of either a single atrial extrastimulus, applied at a critical time after the tachycardia-initiating stimulus (or stimuli), or a train of stimuli. In all 11 patients, reentrant tachycardia was reproducibly induced from the high right atrium with a single premature beat, and in all patients initiation of tachycardia was prevented from the same site by a second premature beat. This second extrastimulus was effective if delivered within a zone which began 10 ms outside the effective refractory period of the tachycardia-initiating stimulus and averaged 61 ms in width. This was termed the 'preventive zone'. In 7 patients the effect of train stimulation to the high right atrium was studied. In all 7, the results were concordant with those obtained by single-beat stimulation. Any train which achieved single atrial capture within the preventive zone was effective in preventing tachycardia. Prevention was always possible with a single atrial extrastimulus or with single-capture train stimulation, whereas termination of an ongoing tachycardia required at least 2 atrial extrastimuli, or stimulation from the right ventricle.

Tachycardia prevention by programmed stimulation

Ten patients with an atrioventricular accessory pathway were studied by standard electrophysiologic techniques to determine if reentrant tachycardia can be prevented in these patients by delivery of a single extrastimulus, applied at a critical time after the tachycardia-initiating stimulus (or stimuli). In all 10 patients, reentrant tachycardia was reproducibly induced from the high right atrium with a single premature beat, and initiation of tachycardia could be prevented from the same site by a second premature beat. This second extrastimulus was effective if delivered within a zone that began 10 ms outside of the effective refractory period of the tachycardia-initiating stimulus and averaged 50 ms in width. This zone was termed the "preventive zone." The width of the preventive zone was independent of the initial tachycardia interval and the tachycardia cycle length. Prevention of reentrant tachycardia was always possible with a single atrial extrastimulus, whereas termination of the ongoing tachycardia required at least 2 atrial extrastimuli or stimulation from the right ventricle.

Electrophysiologic and clinical effects of intravenous and oral encainide in accessory atrioventricular pathway

The effect of intravenous and oral encainide was studied in 12 patients with an accessory atrioventricular pathway (AP). Eight patients had Wolff-Parkinson-White syndrome and 4 had a concealed AP. Electrophysiologic studies were performed before and after intravenous encainide, 1.0 to 1.5 mg/kg, and 4 weeks after oral encainide, 75 to 200 mg/day. Mean follow-up was 19 +/- 6 months. During sinus rhythm, intravenous and oral encainide significantly prolonged the AH and HV intervals. In patients with Wolff-Parkinson-White syndrome, after intravenous encainide, anterograde conduction over the AP was blocked in 3 patients, and the anterograde effective refractory period (ERP) of the AP was markedly increased in 3. Five of these 6 patients had a control value of the anterograde AP ERP of less than 270 ms. Anterograde AP block was maintained in 2 patients after oral encainide therapy. Retrograde AP block or marked increase of retrograde AP ERP was seen in 4 of 9 patients after intravenous encainide and in 2 of 7 after oral therapy. Encainide either prevented induction of circus movement tachycardia (intravenous, 4 of 11 patients; oral, 2 of 7 patients) or significantly prolonged tachycardia cycle length (intravenous, 7 of 11 patients; oral, 5 of 7 patients). During long-term follow-up of 9 patients, 6 patients had no recurrences of tachyarrhythmia after individual adjustment of encainide dosage. One patient had worsening of supraventricular tachycardia after intravenous encainide therapy and 4 patients complained of visual blurring; in 1 patient it was so severe that it required withdrawal of the drug.(ABSTRACT TRUNCATED AT 250 WORDS)

[Electrophysiologic determination of 3 intranodal pathways using various time intervals]

Programmed electrical stimulation of the heart was performed in a 40-year-old man with documented recurrent, sustained ventricular tachycardia, which had proved refractory to standard medical therapy. In this patient, both the presence of several discontinuities in the atrioventricular (AV-)nodal conduction curves during atrial and ventricular stimulation and the varying time intervals of the AV-nodal echo phenomena suggested the presence of multiple AV-nodal pathways.