Jürg Schlaepfer

Clinical efficacy of radiofrequency current in the treatment of patients with atrioventricular node reentrant tachycardia

Eight women (mean age 41 years, range 24 to 62) with drug-resistant atrioventricular (AV) node reentrant tachycardia underwent radiofrequency catheter ablation. Radiofrequency energy was delivered in a unipolar mode with use of a back paddle as the anode placed between the two scapulae. The total applied energy was 2,233 +/- 1,919 J. The AH interval increased from 87 +/- 13 to 113 +/- 17 ms (p less than 0.05) and the PQ interval increased from 141 +/- 15 to 169 +/- 34 ms (p less than 0.05). The anterograde Wenckebach cycle length increased from 300 +/- 41 to 320 +/- 42 ms (p less than 0.05). Retrograde conduction was abolished in five patients. Atrioventricular node tachycardia was still inducible in three patients. During a follow-up period of 9 +/- 3 months, four patients remained clinically asymptomatic without drug therapy and four patients had recurrent symptoms. Three of the latter responded to previously unsuccessful antiarrhythmic drugs and the fourth patient underwent surgical cure for persistence of tachycardia. Right bundle branch block occurred in five patients; it was permanent in four and transient in one. In conclusion, radiofrequency catheter ablation represents a valuable but still investigational therapy in patients with drug-refractory AV node reentrant tachycardia.

Autonomic Imbalance Assessed by Heart Rate Variability Analysis in Vasovagal Syncope

In this prospective study, the autonomic modulation of the sinus node of 12 patients (mean age 28 ± 7 years) suffering from vasovagal syncope (VVS) was compared to that of 11 sex and age matched control patients (mean age 32 ± 4 years) by analysis of heart rate variability. Spectral indices (low frequency power [Plf], high frequency power [Phf], total power [Pt], sympathovagal balance [LF/HF]) and temporal indices, the mean of all coupling intervals between normal beats (mRR), the standard deviation about the mean (sdRR), the percentage of adjacent R to R intervals differing by more than 50 msec (pNN50), and the root mean square of variations in successive R to R intervals (rMSSD) were compared at baseline and during head‐up tilt between and within groups. Baseline results were similar in both groups. During tilt testing, comparison of results between groups revealed only significantly higher sdRR and rMSSD and lower LF/HF ratio in VVS patients. Within WS patients, comparison of temporal and spectral analysis between baseline and tilt showed a significant increase of most indices (Plf, Phf, Pt, sdRR, and rMSSD) but a comparable LF/HF ratio; in contrast, control patients exhibited only a significant increase of LF/ HF ratio. In conclusion. VVS patients who developed vasovagal syncope during head‐up tilt demonstrated a nonreciprocal modulation of the sinus node by the autonomic nervous system indicative of a pronounced physiological sympathetic surge along with a paradoxical vagal input to the cardiovascular system.

Ventricular arrhythmia in coronary artery disease: limits of a risk stratification strategy based on the ejection fraction alone and impact of infarct localization

AIMS Estimates of the left ventricular ejection fraction (LVEF) in patients with life-threatening ventricular arrhythmias related to coronary artery disease (CAD) have rarely been reported despite it has become the basis for determining patients eligibility for prophylactic defibrillator. We aimed to determine the extent and distribution of reduced LVEF in patients with sustained ventricular tachycardia or ventricular fibrillation. METHODS AND RESULTS 252 patients admitted for ventricular arrhythmia related to CAD were included: 149 had acute myocardial infarction (MI) (Group I, 59%), 54 had significant chronic obstructive CAD suggestive of an ischaemic arrhythmic trigger (Group II, 21%) and 49 patients had an old MI without residual ischaemia (Group III, 19%). 34% of the patients with scar-related arrhythmias had an LVEF > or =40%. Based on pre-event LVEF evaluation, it can be estimated that less than one quarter of the whole study population had a known chronic MI with severely reduced LVEF. In Group III, the proportion of inferior MI was significantly higher than anterior MI (81 vs. 19%; absolute difference, -62; 95% confidence interval, -45 to -79; P < or = 0.0001), though median LVEF was higher in inferior MI (0.37 +/- 10 vs. 0.29 +/- 10; P = 0.0499). CONCLUSION Patients included in defibrillator trials represent only a minority of the patients at risk of sudden cardiac death. By applying the current risk stratification strategy based on LVEF, more than one third of the patients with old MI would not have qualified for a prophylactic defibrillator. Our study also suggests that inferior scars may be more prone to ventricular arrhythmia compared to anterior scars.

Acute and Long-Term Ventricular Stimulation Thresholds with a New, Iridium Oxide-Coated Electrode

Efforts have been made to design electrodes that significantly reduce not only the acute and chronic stimulation thresholds, but also attenuate the early peaking phenomenon and polarization. At two voltage levels (2.7 V and 5.4 V, respectively), we evaluated the right ventricular stimulation thresholds obtained with a new, iridium oxide‐coated electrode in ten patients who received a VVI pacemaker. Measurements were mode at implant and at multiple intervals for 1 year. Pulse width stimulation thresholds at implant were as follow: 0.04 ± 0.008 msec at 2.7 V, 0.03 ± 0.004 msec at 5.4 V; values at 2 weeks were 0.14 ± 0.06 msec at 2.7 V, 0.07 ± 0.025 msec at 5.4 V; values at 3 months were 0.09 ± 0.03 msec at 2.7 V, 0.05 ± 0.01 msec at 5.4 V; values at 1 year were 0.08 ± 0.02 msec at 2.7 V, 0.04 ± 0.01 msec at 5.4 V, The maximal increase of 0.11 ± 0.05 msec occurred at 2.7 V, 2 weeks after implant. Our results indicate that this new electrode provides low acute and long‐term stimulation thresholds, as well as an attenuated early peaking phenomenon, being able to stimulate safely at 2.7 V even early after implant.

Evidence rather than costs must guide use of the implantable cardioverter defibrillator

Randomized controlled trials have shown superior survival rates with implantable cardioverter defibrillators (ICDs) compared with antiarrhythmic drugs in survivors of cardiac arrest and life-threatening ventricular tachyarrhythmias, as well as in high-risk patients with ischemic heart disease and inducible ventricular tachycardia (VT). Current defibrillators are small and implanted with techniques similar to standard pacemakers. They provide high-energy shocks for ventricular fibrillation (VF) and rapid VT, antitachycardia pacing for monomorphic VT, and antibradycardia pacing. Limited evidence suggests that ICD therapy is cost-effective when compared with other widely accepted treatments. The use of ICDs is likely to continue to expand in the future. Ongoing clinical trials will define further prophylactic indications of the ICD and clarify its cost-effectiveness ratio in different clinical settings.

Relation Between Cycle Length, Volume, and Pressure in Type I Atrial Flutter

Assuming that type I atrial flutter is a macroreentrant circuit, its cycle length should vary with the atrial dimensions. In order to test this hypothesis, flutter cycle length was measured while inducing atrial volume and pressure changes by postural and pharmacological means in seven patients undergoing a therapeutic programmed stimulation for type 1 atrial flutter conversion. Right atrial volume was estimated from B‐mode echocardiography data. Basal values were compared with those obtained during inspiration, expiration, Valsalva maneuver, negative tilt (head down), and positive tilt (head up) with 0.8–1.6 mg p.o. nitroglycerin. The right atrial size increased slightly from 17.8 to 18.3 cm2 (P = 0.04) during the pressure load induced by negative tilt (+ 3 mmHg), with a corresponding lengthening of the flutter cycle length from 228 to 233 msec (P = 0.02). Similarly, pressure unloading of ‐2 mmHg by positive tilting and nitrates was accompanied by a decrease in right atrial size to 16.6 cm2 (P = 0.04), with a corresponding decrease in cycle length from 228 to 219 msec (P = 0.03). Respiratory maneuver yielded similar results with an inspiratory cycle lengthening, expiratory shortening, and further shortening during Valsalva maneuver. These experiments demonstrate a direct relation between cycle length and atrial volume in human type I atrial flutter. They underline the importance of the right heart preload and atrial size for the electrophysiological characteristics of type I atrial flutter. Beside its fundamental interest, this finding is important for the understanding of the mechanism of maintenance and therapeutic responses of this common arrhythmia.

Competency in interpretation of 12-lead electrocardiogram among Swiss doctors.

One ECG from the survey. Description and MCQ are provided before voting. Diagnosis and comments are given after the vote. Description: Basic rhythm: sinus rhythm, regular at 50 bpm. P waves: normal, but every second wave is blocked. PR interval: normal. QRS: normal duration, increased amplitude from V4 to V6, normal axis. ST segment: isoelectric. T waves: normal. QT interval: prolonged (510 ms). MCQ: 1. Normal sinus rhythm 2. Second degree AV block 3. Long QT syndrome and second degree AV block 4. Long QT syndrome 5. U wave and normal sinus rhythm Diagnosis: Congenital long QT syndrome with functional 2:1 AV block. (Number 3) Comments: The long QT syndrome prolongs the refractory phase of the AV conduction pathways, which explains why a portion of the P waves (which are clearly visible on the descending portion of the T wave) is blocked. In the time it takes for the next excitation to occur, the conduction pathways have completed the refractory phase and the atrioventricular sequence returns to normal. The P waves are not completely regular, since the PP interval with a QRS complex is slightly shorter than the PP interval without a QRS complex. This is owing to an ill-explained phenomenon called “ventriculophasic variation”. do cardiologists [1]. There have been many proposals to optimise training, testing and competency in interpretation of ECGs. However, despite several earlier consensus-based recommendations regarding ECG interpretation, substantive evidence on the training needed to obtain and maintain ECG interpretation skills is not available. Previous recommendations proposed to improve ECG knowledge are not derived from clinical practice or clinical trials [2]. Recently, computerised interpretation and computerised ECG databases have been tested and shown to decrease the number of false ECG interpretations by up to 29% [3, 4]. However, these have shown less accuracy than physician interpreters and must be relied upon only as an adjunct interpretation tool for trained providers. Interpretation of ECGs varies greatly even among expert electrocardiographers. Noncardiologists seem to be more influenced by patient history when interpreting ECGs. Cardiologists appear to perform better than other specialists in standardised ECG examinations when minimal patient history is provided. We tried to understand better the level of knowledge of ECG interpretation of Swiss doctors through the use of an Internet survey. Every 2 weeks a 12-lead ECG was submitted to physicians via an Internet platform exclusively reserved for physicians. A team of three cardiologists chose test ECGs representing daily practice (exceptional or very difficult ECGs were excluded). A short medical history and a description of the ECG were provided. Physicians had to choose independently the correct answer in a multiplechoice question (MCQ) system (fig.). During a 26-month period, 63 traces were submitted. Because the answer had to be given using an MCQ, the expected correct answer score was estimated at approximately 66% (two-thirds of the number of participants). Internists and general practitioners represented 60% of the participants, intensivists 18%, anaesthetists 16% and various other specialists 6%. The mean number of participants was 161 (range 60 to 240). Overall (all groups of specialists and ECG categories combined), the mean number of correct answers was only 31% (range 8 to 76%). Even if we accept the limitations of an internet survey analysis, the percentage of cor-

Electrophysiologic effects of intravenous propafenone at rest, during isoproterenol infusion and during exercise in the Wolff-Parkinson-White syndrome

Abstract Propafenone, a class Ic antiarrhythmic agent, 1 has been shown to be effective in restoring sinus rhythm in patients with symptomatic orthodromic tachycardia associated with Wolff-Parkinson-White syndrome (WPW). 2,3 The high rate of conversion to sinus rhythm (>60%) is attributed to the relatively high dose administered (2 mg/kg). In addition, recurrence of tachycardia can be prevented in most cases. The effectiveness of the antiarrhythmic agent is usually tested at rest. Information concerning the pharmacologic effects of drugs during exercise in patients with supraventricular arrhythmias is scarce. In this study, the electrophysiologic effects of propafenone were examined in 10 patients with WPW at rest, during isoproterenol infusion and during exercise to evaluate its antiarrhythmic properties under these conditions.