The role of the ICD in patients with dilated and hypertrophic cardiomyopathy.
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Cardiomyopathy, Dilated↗
Biomedical subjects
W Haverkamp
Publications and source records attributed to W Haverkamp.
Efficacy of antiarrhythmic drugs in patients with arrhythmogenic right ventricular disease. Results in patients with inducible and noninducible ventricular tachycardia.
BACKGROUND: Ventricular tachyarrhythmias are the major clinical manifestation of arrhythmogenic right ventricular disease. Although antiarrhythmic therapy has been widely advocated, there is only limited information available on the efficacy of antiarrhythmic drugs in these patients. METHODS AND RESULTS: The short- and long-term efficacies of various antiarrhythmic agents were retrospectively and prospectively analyzed in 81 patients (mean age, 39 +/- 14 years; range, 16-68 years; 61.7% males) with arrhythmogenic right ventricular disease. In 42 patients with inducible ventricular tachycardia during programmed ventricular stimulation, the following efficacy rates were obtained: class Ia and Ib drugs (n = 18), 5.6%; class Ic drugs (n = 25), 12%; beta-blockers (n = 8), 0%; sotalol (n = 38), 68.4%; amiodarone (n = 13), 15.4%; verapamil (n = 5), 0%; and drug combinations (n = 26), 15.4%. Only one of the 10 patients not responding to sotalol was treated effectively by amiodarone, whereas the remaining nine patients proved to be drug refractory toward all other drugs tested (3.8 +/- 2.3 drugs, including amiodarone in five cases) and underwent nonpharmacological therapy. During a follow-up of 34 +/- 25 months, three of the 31 patients (9.7%) discharged on pharmacological therapy had nonfatal recurrences of ventricular tachycardia after 0.5, 51, and 63 months, respectively. In 39 patients with noninducible ventricular tachycardia during programmed ventricular stimulation, the following efficacy rates were observed: class Ia and Ib drugs (n = 16), 0%; class Ic agents (n = 23), 17.4%; beta-blockers (n = 7), 28.6%; sotalol (n = 35), 82.8%; amiodarone (n = 4), 25%; verapamil (n = 24), 50%; and drug combinations (n = 11), 9.1%. During a follow-up of 14 +/- 13 months, four of 33 patients (12.1%) discharged on antiarrhythmic drugs had nonfatal relapses of their clinical ventricular arrhythmia. CONCLUSIONS: Thus, in arrhythmogenic right ventricular disease, sotalol proved to be highly effective in patients with inducible as well as noninducible ventricular tachycardia. Patients with inducible ventricular tachycardia not responding to sotalol are likely to not respond to other antiarrhythmic drugs and should be considered for nonpharmacological therapy without further drug testing. Amiodarone did not prove to be more effective than sotalol and may not be an alternative because of frequent side effects during long-term therapy, especially in young patients. Verapamil and beta-blockers were effective in a considerable number of patients with noninducible ventricular tachycardia and may be a therapeutic alternative in this subgroup. Class I agents appear to be rarely effective in the treatment of both inducible and noninducible ventricular tachycardia in arrhythmogenic right ventricular disease.
Adolescent↗
How to evaluate class III antiarrhythmic drug efficacy clinically: the benefits and shortcomings of the invasive approach.
Ventricular tachycardia and ventricular fibrillation are frequent complications of organic heart disease. There is sufficient evidence that serial electrophysiologic testing is able to predict long-term efficacy of antiarrhythmic agents in patients with malignant ventricular tachyarrhythmias. This approach has not only been useful for the evaluation of class I drugs, but recent studies have shown that this invasive method may also be useful for the management of patients undergoing treatment with class III antiarrhythmic agents such as amiodarone and sotalol. The results of several studies suggest that class III agents are more effective than class I drugs in patients presenting with ventricular tachycardia or ventricular fibrillation. Proarrhythmic complications in patients treated with class III antiarrhythmic drugs are mainly characterized by torsades de pointes. Their incidence does not exceed 5%. Further studies are necessary to elucidate the mechanisms underlying this type of proarrhythmia. By the use of currently available stimulation techniques, patients who might develop torsades de pointes while on therapy with a class III agent cannot be identified.
Amiodarone↗
[Initial presentation of ventricular pre-excitation after catheter ablation of concealed retrograde conducting accessory atrioventricular pathways].
Catheter ablation using radiofrequency or direct current energy was performed in 19 consecutive patients with concealed accessory pathways. Four patients developed manifest preexcitation for the first time following ablation. The concealed accessory pathways of these four patients were localized at right lateral, left posteroseptal, left posterolateral, and left lateral sites, respectively. In two patients, manifest preexcitation developed immediately after attempted ablation. In the other two patients, preexcitation occurred after 4 and 14 days. Electrophysiologic testing revealed in all four patients that the origin of manifest preexcitation corresponded to the site of the concealed pathway. Successful catheter ablation using radiofrequency current was performed in three patients. One patient preferred surgical interruption of the accessory pathway. The reason for this sudden emergence of preexcitation of these patients with only retrograde conducting pathways remains to be investigated. The anterograde conduction capacity might have been modified by damaging the site of the accessory pathway insertion.
Adult↗
[Percutaneous high frequency current catheter ablation in permanent ventricular tachycardia of the "bundle-branch reentry" type after implantation of an automatic cardioverter-defibrillator].
A 65-year-old female patient with a history of recurrent sustained ventricular tachycardia presented with an incessant ventricular tachycardia (cycle length 360-400 ms) following implantation of a cardioverter-defibrillator (ICD). The tachycardia could not be terminated by antiarrhythmic drug treatment, antitachycardia pacing or internal defibrillation via the ICD. An invasive electrophysiologic study revealed that the mechanism of this newly occurring tachycardia was bundle branch reentry. The patient underwent emergency catheter ablation using radiofrequency (RF) current. Endocardial mapping of the right bundle branch and of the distal His bundle was performed and a bundle branch reentry tachycardia was diagnosed. After delivery of the fifth RF-impulse, the tachycardia terminated and complete AV block was induced. No malfunction of the ICD was observed following RF-ablation. The patient was hemodynamically stable with a junctional escape rhythm and antibradycardia pacing back-up of the ICD (VVI-mode). This case report demonstrates the feasibility of RF catheter ablation in the treatment of incessant bundle branch reentry tachycardia as a complementary option after implantation of an ICD.
Aged↗
[High frequency current catheter coagulation using pulsed energy delivery. Results with isolated myocardial tissue].
The feasibility and efficacy of pulsed radiofrequency (RF) current delivery was assessed and compared to results obtained by continuous energy delivery. Energy was delivered to ventricular preparations of isolated porcine hearts (HAT 100, 500 kHz, Osypka, FRG). In the pulsed mode, impulse duration and pause duration were varied between 50 and 500 ms. Total duration of coagulation was 30 s in all cases. The depth of induced lesions was significantly enhanced by a short impulse- and pause duration (50-70 ms) compared to continuous RF energy delivery. At long pause durations (200-500 ms) and short impulse duration, depth and diameter of lesions significantly decreased. The incidence of sudden increases in impedance was markedly attenuated when energy was delivered discontinuously. Thus, pulsed RF energy delivery can be used to enhance the depth of RF lesions. The decreased incidence of sudden rises in impedance during pulsed energy delivery further enhances the feasibility of RF coagulation. An improvement in heat transfer to deeper tissue layers can be considered as the mechanism responsible for these effects.
Animals↗
[Biophysical aspects of high frequency catheter ablation. Studies of the significance of sudden changes in impedance].
UNLABELLED: To determine the effects and the underlying mechanisms of sudden rise of impedance during radiofrequency (RF) catheter ablation, 60 RF applications were delivered to isolated preparations of ventricular myocardium at three different power levels (mean: 3.7, 11.3, 19.3 watts). Pulse duration was 30 s, current voltage and catheter tip temperature were continuously monitored. Impedance rise occurred during 34 of 60 applications; the incidence of impedance rise increased at higher power levels. Impedance rise was significantly more often observed when the preparations were superfused with heparinized blood compared to saline solution (p less than 0.05). Catheter-tip temperature during radiofrequency application without impedance rise was significantly lower compared to applications with impedance rise (mean = 108 degrees C vs. 121 degrees C, p less than 0.01). The increase of catheter-tip temperature and maximal-tip temperature following impedance rise was significantly higher in blood when compared to saline solution (mean = +48 degrees C vs. +13 degrees C (p less than 0.001), Tmax: 121 degrees C vs. 245 degrees C). Following impedance rise, insulation defects of the electrode catheter and vaporized crater formation of the myocardium was often observed. CONCLUSIONS: During radiofrequency catheter ablation impedance rise occurs following overheating of the catheter electrode (greater than 110 degrees C). After impedance rise, catheter-tip temperature markedly increases. Insulation defects of the catheter and vaporized craters in the myocardium frequently occur after impedance rise. The results have important implications for the clinical use of RF-currents for catheter ablation; energy application should be immediately stopped after the occurrence of impedance rise.
Animals↗
[Catheter ablation of ventricular tachycardia].
Catheter ablation of ventricular tachycardias was performed in a total of 80 patients whose tachycardias were considered as drug refractory and who were not considered to be candidates for antitachycardic surgery or implantation of an automatic cardioverter defibrillator. After careful endocardial catheter mapping including pacing interventions, either direct-current (DC) (n = 61) or radiofrequency current (RF) (n = 13) or both (n = 6) were applied of the "site of origin" of ventricular tachycardia or the "zone of slow conduction". 42 of 51 patients with coronary heart disease were discharged; ventricular tachycardia recurred in 8 cases, and 2 patients died suddenly. In the remaining 32 patients, there were no recurrences of ventricular tachycardia during a mean follow-up period of 12 month. Three patients died perioperatively. In 21 of 29 patients without coronary artery disease, no recurrences of ventricular tachycardia were observed (mean duration of follow-up 17 months) whereas 8 cases had a recurrence of ventricular tachycardia.
Cardiac Catheterization↗
Catheter ablation of ventricular tachycardia using radiofrequency current.
Catheter ablation techniques have evolved as an alternative to map-guided surgery and proven effective in a variety of supraventricular tachyarrhythmias. Direct current catheter ablation has been shown to be effective in about 50 to 70% of cases. Approximately, 60% of patients with structural heart disease and monomorphic ventricular tachycardia were successfully treated using direct current ablation techniques. This overall success rate and possible risks associated with the use of direct current have stimulated the search for other energy sources appropriate for catheter ablation. Presently, only a few preliminary reports on the clinical efficacy of radiofrequency energy for the treatment of ventricular tachyarrhythmias in man exist. 23 patients with identifiable heart disease at a mean age of 52 +/- 17 years underwent radiofrequency catheter ablation. 16 patients had coronary artery disease, one patient dilative cardiomyopathy and six patients had arrhythmogenic right ventricular disease. All patients presented with chronic current sustained ventricular tachycardia. After detailed endocardial catheter mapping radiofrequency energy was applied at the site of earliest ventricular activation during ventricular tachycardia which could be entrained during fixed rate ventricular pacing at the site of origin of ventricular tachycardia. At all ablation sites a long latency between the stimulus and QRS complex was noted. Of 23 patients 18 were treated with radiofrequency alone whereas in five patients a second ablation procedure using direct current was performed. Following the ablation procedures, 14 patients (61%) remained free of ventricular tachycardia. One patient died due to congestive heart failure 21 months following ablation.(ABSTRACT TRUNCATED AT 250 WORDS)
Cardiac Catheterization↗
Cardiopulmonary effects of constant-flow ventilation in experimental myocardial ischaemia.
The cardiopulmonary effects of constant-flow ventilation were investigated in dogs with normal heart function (control-phase, n = 14) and after development of acute myocardial ischaemia (ischaemia phase, n = 14). Heated, humidified and oxygen-enriched air was continuously delivered with an inspiratory flow rate of 1.21.kg-1.min-1 via two catheters positioned within each mainstem bronchus. Continuous positive pressure ventilation with a positive end-expiratory pressure of 0.5 kPa (5 cmH2O) was used as a reference. During control, neither continuous positive pressure ventilation nor constant-flow ventilation showed impairment of cardiopulmonary performance. Oxygenation and CO2 removal were more efficiently achieved by continuous positive pressure ventilation (P less than or equal to 0.05). Acute myocardial ischaemia was induced by occlusion of the left anterior descending (LAD) coronary artery; measurements during the ischaemia phase were performed 60 min following LAD occlusion. Myocardial ischaemia resulted in moderate changes of cardiac output, left ventricular end-diastolic pressure and dP/dtmax. Both modes of ventilation were well tolerated in the ischaemia phase, and cardiovascular performance revealed no significant differences between continuous positive pressure ventilation and constant-flow ventilation. Haemodynamic parameters could be more precisely assessed during constant-flow ventilation. Oxygenation deteriorated, but hypoxaemia did not occur in any animal and CO2 elimination remained unchanged. It is concluded that 'non-conventional' ventilation by continuous intrabronchial gas flow maintains adequate gas exchange with no adverse effects on haemodynamics in dogs with acute myocardial ischaemia. Constant-flow ventilation may be advantageous in the experimental setting to study cardiac function without cyclic heart-lung interaction due to airway pressure alterations.
Animals↗
Sodium channel blockers in the treatment of ventricular arrhythmias: different effects in the normal, ischaemic or failing heart?
In past decades, numerous experimental and clinical studies have improved our knowledge of the electrophysiological effects of sodium channel blockers, as well as of the mechanisms of arrhythmogenesis. However, the mechanisms of antiarrhythmic as well as potentially proarrhythmic drug action have been less well clarified. Sodium channel blocker agents have different effects on the normal, ischaemic, and failing heart since their antiarrhythmic actions depend on the substrate and the mechanisms of arrhythmogenesis, as well as other mostly interrelated cardiac and non-cardiac factors. Strict criteria of efficacy and safety have to be applied when sodium channel blockers are used for the treatment of ventricular arrhythmias.
Anti-Arrhythmia Agents↗
[Non-pharmacological treatment of arrhythmia using the method of trans-catheter ablation].
Trans-catheteral ablation is an important therapeutic method for nonpharmacological management of various types of cardiac arrhythmias. Since its introduction into clinical practice in 1982, it has proved its efficacy in disturbance or change of the type of atrioventricular conduction and conduction along accessory abnormal atrioventricular conduction pathways. Positive results have also been attained in the treatment of some patients with ventricular tachycardia. The energy sources used for ablation include direct current pulses possessing large energy, high-frequency currents, and laser energy. Ablation with direct current and high-frequency current is already used successfully in patients, while the use of laser energy for ablation of myocardial arrhythmogenic tissue is limited mainly to operations on the open heart. The use of alternating high-frequency current has attracted particular attention in the last years. Trans-coronary chemical ablation is another recently introduced method which is not connected with the use of electric current. Only experimental and a small clinical experience with this new method has been gained to date. This survey systemasizes the current knowledge of the biophysical bases of the various method of ablation from the standpoint of the mechanisms of treatment, the methodology and the main types of tissue response. Clinical experience with trans-catheteral treatment of cardiac arrhythmias is analysed.
Arrhythmias, Cardiac↗
[Percutaneous endocardial Nd-YAG laser energy: experimental studies of ablation of the ventricular myocardium].
The in vitro and in vivo effects of endocardial laser ablation were assessed. Energy was supplied by a Nd-YAG laser (wavelength approximately 1064 nm) and transmitted via a quartz core fiber (phi: 0.4 mm) housed within a specially designed 7 F catheter. In vitro, the effects of increasing output power (5, 10, 20, 40 watt) and impulse duration (1, 2, 4, 8 s) on lesion size were assessed in myocardial preparations of canine hearts. Preparations were superfused with saline or blood, respectively; the distance of the optical fiber to the endocardium was 5 mm. Lesion size increased in diameter (range: 0-4.0 mm) and depth (range: 0-5.2 mm) in a power- and time-dependent manner. Superfusion with blood significantly enhanced the diameter of the lesions, whereas depth of the lesions significantly decreased. In 16 anesthetized mongrel dogs, a total of 52 laser impulses (output power: 10, 20, 40 w; impulse duration: 1, 2, 4 s; energy: 10-160 J) were delivered to apical and apico-inferior sites of the left ventricle. Postmortem, 40 lesions with a diameter of 2.6-19.4 mm and a depth of 3.7-16.2 mm were found. 19 lesions revealed central vaporized craters with a depth up to 11.2 mm. Perforation of the left ventricle occurred in two cases following 80 and 160 J, respectively. In vitro and in the intact animal (in apical and apico-inferior sites of the left ventricle) endocardial laser ablation is feasible to induce distinct myocardial lesions in a power- and time-dependent manner.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Catheter ablation using radiofrequency energy.
Recently, transvenous catheter ablation using radiofrequency impulses has been applied in experimental animals as well as in humans. This review describes the biophysics, mechanisms, and tissue effects of radiofrequency alternating current. Ablation of the AV-junction has been performed in experimental studies as well as in a growing number of patients. Complete AV-block or modification of the AV conduction by RF-current application can be achieved in about 45-65% of patients. Presently about 50% of patients with rightsided accessory pathways can be successfully managed using radiofrequency impulses. Certain limitations exist using a biopolar "epi-endocardial" electrode configuration for leftsided accessory pathways. Only few studies are available concerning the use of RF ablation of ventricular tachycardia foci. As most experimental investigations were carried out in structurally nondiseased myocardium, the use of this new technique in fibrotic or scarred tissue warrants further studies. Radiofrequency catheter ablation seems to be feasible and relatively safe for the treatment of otherwise drug-refractory supraventricular arrhythmias; further studies are needed to assess the safety and efficacy in patients with drug-refractory ventricular tachyarrhythmias.
Animals↗
Effects of beta-blockade on the incidence of ventricular tachyarrhythmias during acute myocardial ischemia: experimental findings and clinical implications.
Myocardial ischemia and infarction are the most common substrates for life-threatening ventricular tachyarrhythmias. Experimental and clinical evidence suggests that enhanced activity of the sympathetic nervous system plays an important role in the genesis of ischemia-related arrhythmias. In animal experiments, beta-blockers display significant antifibrillatory effects during the acute phase of myocardial ischemia. Preconditions for their antifibrillatory effects are high serum- and tissue-concentrations, and absence of a significant partial agonist activity. During the delayed phase of ischemic arrhythmias which starts 6-8 h after coronary occlusion, beta-blockers gain significance as antiarrhythmic and potentially antifibrillatory drugs, if sympathetic activity is enhanced. The presently available evidence suggests that the potentially antifibrillatory effects of beta-blockers are at least one of the major mechanisms by which these drugs may decrease mortality when given prophylactically in patients after myocardial infarction. However, it remains to be explained why beta-blockers, in a great number of prospective randomized trials, have reduced the incidence of sudden death only by an average of about 30%. This may be the result of their "specific" mechanisms acting in the setting of acute myocardial ischemia with enhanced adrenergic tone, whereas in the remaining patients other mechanisms such as a chronic arrhythmogenic substrate may be operative. A clearer separation of these various mechanisms seems mandatory in order to allow a more specific "targeted" administration of beta-blockers. This is the more important since none of the available prospective studies that used antiarrhythmic agents has shown an improvement of prognosis, but, instead showed a worsening of the mortality rate.
Adrenergic beta-Antagonists↗
Antiarrhythmic properties of beta-blockers.
Beta-blockers are effective antiarryhthmic agents for certain types of supraventricular and ventricular arrhythmias. They are able to prevent arrhythmias associated with sympathetic hyperactivity, suppress automaticity, and slow conduction in myocardial tissue with predominant slow-response activity. In animal experiments, beta-blockers have been shown to exert pronounced antifibrillatory effects following occlusion of a main coronary artery. This effectiveness may be the basis for the improved survival of patients with chronic coronary artery disease under long-term beta-blockade. Side effects are often dose-related; the optimal and minimal effective doses of the beta-blocker are critical in limiting adverse effects. As conventional antiarrhythmic agents have not been shown to reduce the risk of mortality in postmyocardial infarction patients, a broader application of beta-blockers as antiarrhythmic agents within the future, possibly in combination with class I or III drugs, seems conceivable.
Adrenergic beta-Antagonists↗
Radiofrequency coagulation of ventricular myocardium: improved prediction of lesion size by monitoring catheter tip temperature.
To assess the importance of voltage, current, impedance and catheter tip temperature for the prediction of the size of tissue injury induced by transcatheter radiofrequency application, radiofrequency pulses (500 kHz) were delivered both in vitro and in vivo to isolated ventricular preparations and the intact canine heart, respectively. Radiofrequency coagulations were performed using unipolar electrode configuration. Besides measurements of current and voltage which were used to calculate the delivered power and tissue impedance, the catheter tip temperature was monitored during each application using specially designed 6F USCI catheters with a built-in nickel/chromium-nickel thermoelement. Lesion dimensions were measured and the correlation between lesion volume and delivered radiofrequency energy, maximum changes in catheter tip temperature and the integral of the temperature curve were calculated. First, in a pilot in vitro investigation, 50 radiofrequency coagulations (3.2 W-22.4 W, pulse duration 10 s) were performed in ventricular preparations from freshly excised dog hearts. The correlation between applied radiofrequency energy and lesion volume was 0.87; the correlation between maximal catheter tip temperature and lesion volume was 0.82; the correlation between temperature integral and lesion volume was 0.9. In the intact dog heart, 44 radiofrequency pulses were delivered to the left and right ventricular endocardium in 12 anaesthetized dogs (exposure time: 10 s). Delivered power ranged between 5.6 W and 24.6 W; tissue impedance varied between 92 omega and 364 omega; lesion volume measured 0-273 mm3; developed peak temperatures ranged from 16.25 degrees C to 196 degrees C. The calculated integral beneath temperature curves measured 126-1971 degrees C.s. The correlation between applied radiofrequency energy and lesion volume was 0.32; the correlation between maximal catheter tip temperature and lesion volume was 0.61. Temperature integral correlated best with the assessed volume of myocardial necrosis (r = 0.7). No significant arrhythmogenic or haemodynamic side-effects were observed. Macroscopic examination showed a central depression surrounded by a zone of homogeneous coagulation. Vaporization and crater formation up to a depth of 4 mm were observed following three radiofrequency discharges. In two of these cases, rapid changes and oscillation of catheter tip temperature were observed. Thus, monitoring of catheter tip temperature during radiofrequency energy application improves the prediction of lesion size. In addition, temperature monitoring might improve the safety of the procedure with respect to the risk of perforation.
Animals↗
Coagulation of ventricular myocardium using radiofrequency alternating current: bio-physical aspects and experimental findings.
Within the last years, a variety of different energy sources has been investigated to test their feasibility for catheter ablation of myocardial tissue. This report summarizes our experience of the use of radiofrequency alternating current (500 kHz, unipolar mode) for coagulation of ventricular myocardium in canine experiments. Under standardized in vitro conditions, we found a significant correlation between actually delivered radiofrequency energy and assessed myocardial necrosis (r = 0.87). However, this did not hold for percutaneous application of radiofrequency alternating current to the beating dog heart (r = 0.32). In the intact dog heart, the size of induced lesions paralleled catheter contact pressure which was varied until ST-egment elevation was either 0-2 mV or 5-7 mV. However, no statistical significant differences in either calculated energy or tissue impedance were observed. Under in vivo conditions, a significant improvement in the predictability of the resulting size of lesions was observed when catheter tip temperature, measured via a built-in Ni/CrNi thermoelement, was monitored (r = 0.07). Changes in tip temperature during coagulation also indicated the quality of catheter contact, catheter damage and the appearance of carbonization at the tip of the ablation catheter. Total perforation of the myocardial wall and proarrhythmogenic effects were only rarely observed. In conclusion, catheter coagulation of myocardial tissue using radiofrequency energy can be considered as safe and effective. Since changes in catheter tip temperature occurring during coagulation were found to predict the extent of induced tissue necrosis, the development of temperature controlled radiofrequency devices seems promising and necessary.
Animals↗