Slawomir Weretka

Ventricular oversensing: A study of 101 patients implanted with dual chamber defibrillators and two different lead systems

WERETKA, S., et al. : Ventricular Oversensing: A Study of 101 Patients Implanted with Dual Chamber Defibrillators and Two Different Lead Systems. Modern dual chamber ICD systems are able to overcome various sensing problems. However, improvement of their performance is still required. The aim of this study was to assess the sensing function in 101 consecutive patients (84 men, 17 women; mean age 63 ± 12 years; mean follow‐up 24 ± 4 months) implanted with dual chamber defibrillators and integrated (IB) or dedicated bipolar (DB) lead systems. Follow‐up data were analyzed for the presence of ventricular oversensing. Oversensing occurred in 25 (25%) patients, significantly more frequent in patients implanted with IB compared to DB lead systems (21/52 vs 4/49, P = 0.0002). Patients with cardiomyopathies (CMs) were more prone to sensing malfunctions than patients with no CM (12/30 vs 13/71, P = 0.04). T wave oversensing (n = 14), respirophasic ventricular oversensing (n = 4), and P wave oversensing (n = 6) were the most common pitfalls of ventricular sensing. P wave oversensing was unique to the IB lead system. CT scans performed in these patients disclosed the position of the RV coil to be proximal to the tricuspid area. Four patients received inappropriate ICD shocks due to oversensing. In all but two patients who received lead revision, oversensing was resolved by noninvasive means. In conclusion: (1) ventricular oversensing is a common problem occurring in up to 25% of patients with dual chamber ICDs; (2) P wave oversensing is a ventricular sensing problem affecting function of 11% of dual chamber devices with IB lead systems; (3) IB leads are significantly more susceptible to T wave and P wave oversensing than DB leads; and (4) patients with cardiomyopathies are more prone to oversensing than patients with other heart diseases. (PACE 2003; 26[Pt. I]:65–70)

Bertosamil blocks HERG potassium channels in their open and inactivated states

Bertosamil is chemically related to the class‐III anti‐arrhythmic drug tedisamil and has been developed as a bradycardic, anti‐ischemic and anti‐arrhythmic drug. Its anti‐arrhythmic properties might in part be attributed to its block of voltage‐dependent potassium channels Kv1.2, Kv1.4. and Kv1.5. However, HERG‐potassium channel block as an important target for class‐III drugs has not yet been investigated. We investigated the effect of bertosamil on the HERG potassium channel heterologously expressed in Xenopus oocytes with the two‐electrode voltage‐clamp technique. Bertosamil (70 μM) inhibited HERG tail currrent after a test pulse to 30 mV by 49.3±8.4% (n=5) and the IC50 was 62.7 μM. Onset of block was fast, i.e. 90% of inhibition developed within 180±8.22 s (n=5), and block was totally reversible upon washout within 294±38.7 s (n=5). Bertosamil‐induced block of HERG potassium channels was state‐dependent with block mainly to open‐ and inactivated channels. Half‐maximal activation voltage was slightly shifted towards more negative potentials. Steady‐state inactivation of HERG was not influenced by bertosamil. Bertosamil block elicited voltage–but no frequency‐dependent effects. In summary, bertosamil blocked the HERG potassium channel. These blocking properties may contribute to the anti‐arrhythmic effects of bertosamil in the treatment of atrial and particular ventricular arrhythmias.

Far-field R wave oversensing in a dual chamber arrhythmia management device: predisposing factors and practical implications.

WERETKA, S., et al.: Far‐Field R Wave Oversensing in a Dual Chamber Arrhythmia Management Device: Predisposing Factors and Practical Implications. Initial experience with the Medtronic Jewel 7250, the ICD designed to detect and treat ventricular and supraventricular tachyarrhythmias, is very promising. Its effectiveness, however, depends on sensing performance, which has not yet been systematically examined. The aim of the study was to determine the incidence of, predisposing factors for, and practical implications of far‐field R wave oversensing (FFRWOS) in this dual chamber ICD. During a total follow‐up of 797 months in 48 patients who had the Jewel 7250, follow‐up strip charts, 12‐channel Holter recordings and, in particular cases, Holter recordings with intracardiac markers were analyzed for the presence of FFRWOS. FFRWOS was documented in ten (21.3%) patients. Compared to other lead locations, the right atrial appendage lead position was most frequently associated with FFRWOS (7/27 vs 3/21, P < 0.05). Patients with FFRWOS had significantly more treated and nontreated atrial episodes, many of which were judged to have been detected inappropriately. In one case, inappropriate atrial antitachycardia pacing due to R wave oversensing triggered sustained ventricular tachycardia, terminated eventually with a high energy shock. In dual chamber ICDs, FFRWOS may represent a frequent phenomenon possibly leading to serious consequences. For atrial leads, a lateral atrial wall position seems to be preferable. In most cases, FFRWOS can be eliminated by optimization of atrial sensing parameters. Given the possibility of ventricular proarrhythmia with atrial pacing therapy, the capability of ventricular backup defibrillation in respective devices is at least reassuring.

Variability of Holter Electrocardiographic Findings in Patients Fulfilling the Noninvasive MADIT Criteria

SENGES, J.C., et al.: Variability of Holter Electrocardiographic Findings in Patients Fulfilling the Noninvasive MADIT Criteria. In the MADIT study, a selected group of postinfarction patients with asymptomatic nonsustained ventricular tachycardia (NSVT) has been shown to benefit from prophylactic ICD treatment. The present study analyzed the variability of NSVT in a patient population fulfilling the noninvasive MADIT criteria. Three consecutive Holter ECGs were performed in weekly intervals in 68 postinfarction patients with an LVEF ≤ 0.35. Patients with NSVT underwent programmed ventricular stimulation (PVS); patients were implanted with an ICD if sustained VT or VF was inducible. If NSVT was found in at least two recordings, the arrhythmia was defined as reproducible. In 28 (41%) of the 68 patients, NSVT was found in at least one recording. Seventeen patients revealed NSVT in the first, the remaining 11 in the second registration; no patient had NSVT only in the third Holter. Of the patients with NSVT, 50% had only one, 39% had two, and 11% had three positive recordings. Thus, reproducible NSVT was found in only 50% of the patients with NSVT. Predictors for reproducibility were LVEF > 0.27, NYHA Class I, absence of digitalis therapy, and > 2 NSVT per 24‐hour period. Reproducible NSVT was not associated with risk factors such as elevated mean heart rate, reduced heart rate variability, late potentials, or inducibility of sustained VT during PVS. During 17 ± 9 months of follow‐up, seven (10%) patients experienced arrhythmic events: two without and five with previously documented NSVT. In the latter patients, first occurrence of NSVT was consistently in the first Holter; only two of them had reproducible NSVT. In postinfarction patients, the risk factor NSVT exhibits marked spontaneous variability, especially in those with a low number of NSVT per 24‐hour period, LVEF < 0.27 or NYHA III, which limits its clinical value as a selection criterion for PVS. Reproducibility of NSVT itself does not seem to be an independent risk factor.

Mitral valve endocarditis: an uncommon cause of myocardial infarction.

Die Koronararterienembolie ist eine seltene, aber schwerwiegende Komplikation einer subakut verlaufenden bakteriellen Endokarditis. Eine 39-jährige Patientin mit akutem Vorderwandinfarkt infolge eines distalen Verschlusses des Ramus interventricularis anterior (RIVA) wurde durch Akut-PTCA ohne Stentimplantation erfolgreich (TIMI-III-Fluss) behandelt. Erst nach der Koronarintervention wurde die Diagnose einer subakuten bakteriellen Endokarditis auf Grund von Fieber, Mitralklappenvegetationen in der transoesophagealen Echokardiographie und positiven Blutkulturen für Streptococcus faecalis gestellt. Trotz Antibiogramm-gerechter antibiotischer Therapie war schließlich ein elektiver Mitralklappenersatz erforderlich wegen höhergradiger Mitralklappeninsuffizienz. Bei mehrfachen auswärtigen Untersuchungen wegen fieberhafter Allgemeinsymptomatik wurde die Diagnose nicht gestellt, wohl weil nicht an eine subakute bakterielle Endokarditis gedacht wurde. Erst die lebensbedrohliche Komplikation einer Koronararterienembolie führte schließlich zur richtigen Diagnose. Dieser Fall erinnert eindrücklich daran, dass die Diagnosestellung einer Endokarditis schwierig sein kann und in erster Linie auf deren Einschluss in die Differentialdiagnose basiert. Darüber hinaus liefert er ein Beispiel für eine erfolgreiche Akutrekanalisation bei septisch- embolischem Koronararterienverschluss durch PTCA. A 39 year old woman presented with acute anterior myocardial infarction. At coronary angiography the distal left anterior descending coronary artery (LAD) was occluded despite otherwise normal coronary arteries. The LAD was successfully recanalized using PTCA. Subsequently, a transesophageal echocardiogram revealed vegetations and a significant incompetence of the mitral valve. Blood cultures identified out enterococcus faecalis. Despite intravenous antibiotic treatment guided by sensitivity testing, the patient ultimately required elective mitral valve replacement. During a prior outpatient diagnostic work-up of fever/malaise, the diagnosis of infective endocarditis was not made. This case conveys two main messages: 1) because the history and physical sings of bacterial endocarditis can be subtle or nonspecific, the first step to diagnose infective endocarditis is to include it in the differential diagnosis. 2) Percutaneous coronary intervention is an effective treatment of septic embolic occlusion of a major coronary artery.

Vascular effects of class-III antiarrhythmic drugs: chromanol 293B, but not dofetilide blocks the smooth muscle delayed rectifier K+ channel.

Abstract Chromanol 293B and dofetilide are inhibitors of IKs and IKr, i.e., of the slow and the rapid component of the delayed rectifier potassium current. The specificity of these drugs was tested by investigating their effects on the delayed rectifier potassium current in vascular smooth muscle, regulating the tone of blood vessels. Using depolarizing step protocols with asymmetrical potassium concentrations (135/4.5 mM K+ in pipette/bath), voltage-dependent K+ currents (IKv) of enzymatically dispersed guinea pig portal vein cells were studied in the whole-cell patch-clamp technique. Peak currents were obtained within 20 ms (at +50 mV) after activation. During a 10 s test pulse to +60 mV, these currents exhibited a relatively fast inactivation with time constants of 384 ms (τfast) and 4505 ms (τslow). Dofetilide was totally ineffective in modulating currents; in contrast, after application of chromanol 293B, a steady-state block of IKv developed within 135 s. The block was concentration-dependent with an IC50 of 7.4 μM. Chromanol did not produce any shift in the normalized steady-state activation and inactivation curves and the recovery from inactivation was not significantly changed. Chromanol 293B similarly inhibited delayed rectifier K+ channels whether in their closed or open state, and produced an “apparent” acceleration of inactivation, i.e., the drug accelerated the faster time constant of inactivation during a 10 s test pulse from 384 ms (control) to 149 ms (100 μM chromanol). In recent studies, chromanol was described as a specific blocker of slowly activating delayed rectifier potassium channels (IKs) in cardiomyocytes. The results of this study, however, extend the inhibitory spectrum of the drug and demonstrate block of closed and open state delayed rectifier K+ currents in portal vein vascular smooth muscle. Such a block could possibly contribute to the generation of portal hypertension.

Are Electrophysiological Studies Needed Prior to Defibrillator Implantation

At present, patients with documented sustained VT or resuscitated cardiac arrest (CA) are treated with ICDs. The aim of this study was to retrospectively evaluate if a routine electrophysiological study should be recommended prior to ICD implantation. In 462 patients referred for ICD implantation because of supposedly documented VT (n = 223) or CA (n = 239) , electrophysiological study was routinely performed. In 48% of the patients with CA, sustained VT or VF was inducible. Electrophysiological study suggested conduction abnormalities (n = 11) or supraventricular tachyarrhythmias (n = 3) in conjunction with severely impaired left ventricular function to have been the most likely cause of CA in 14 (5.9%) of 239 patients. Likewise, sustained VT was only inducible in 48% of patients with supposedly documented VT. Of these inducible VTs, nine were diagnosed as right ventricular outflow tract tachycardia or as bundle branch reentry tachycardia. Supraventricular tachyarrhythmias judged to represent the clinical event were the only inducible arrhythmia in 35 (16%) patients (AV nodal reentrant tachycardia [n = 7] , AV reentry tachycardia [n = 4] , atrial flutter [n = 19] , and atrial tachycardia [n = 5] ). Based on findings from the electrophysiological study, ICD implantation was withheld in 14 (5.9%) of 239 patients with CA and in 44 (19.7%) of 223 patients with supposedly documented VT. During electrophysiological study, VT or VF was only reproducible in about 50% of patients with supposedly documented VT or CA. Electrophysiological study revealed other, potentially curable causes for CA or supposedly documented VT in 12.6% (58/462) of all patients, indicating that ICD implantation can potentially be avoided or at least postponed in some of these patients. Based on these retrospective data, routine electrophysiological study prior to ICD implantation seems to be advisable. (PACE 2003; 26:1715–1721)

Effizienzpotential in der Nachsorge von Schrittmachern und implantierbaren Kardioverter Defibrillatoren

SummaryThe aim of the present study was to elucidate whether the duration of a technical follow-up (FU) of a pacemaker (PM)/implantable cardioverter defibrillator (ICD) has an impact on cost-effectiveness in the outpatient clinic. We determined the time required for a complete FU of devices from three different manufacturers.In 130 patients (70 VVI/DDD-PM, 60 VVI/DDD-ICD) with either a PM (Phylos, Chorum/Talent, Kappa, EnPulse) or an ICD (Belos, Alto or GEM) the time was recorded for a complete FU including determination of lead impedance, sensing and pacing threshold. The time for activation of individual menue buttons was excluded. On the basis of time required for FU, cost-units (CU) were calculated for 2000 FU/year and for a presumed device longevity (PM 7 years, ICD 5 years).For VVI-PM, the duration of FU was almost identical for devices from different manufacturers (105±11 s to 125±8 s; p=n.s.). However, analysis of DDD-PM revealed marked differences (140±25 s vs 282±23 s, p<0.05). Time for FU of ICDs varied between 108±5 s and 207±21 s (p<0.05) in VVI-ICDs and between 129±8 ms and 225±23 s (p<0.05) in DDD-ICDs. The total savings could be 55 000 CU in VVI- and 53 333 CU in DDD-ICDs. For full automatic DDD-pacemakers (EnPulse) time for FU could be reduced to 58±3 s (p<0.05). Differences in FU times were caused by problems with telemetry, delay during booting of the programmer, interrogation at the beginning and at the end of FU and for sensing tests.Improving not only programmers and devices but also test automaticity could significantly increase cost-efficiency in the outpatient clinic.ZusammenfassungDie vorliegende Studie untersucht geräteabhängige Kostensenkungspotentiale im Prozess der Nachsorge beim Einsatz verschiedener Schrittmacher (SM) und implantierbarer Kardioverter-Defibrillatoren (ICD).Bei 130 Patienten (n=60 VVI-SM/ICD, n=70 DDD-SM/ICD) mit implantiertem SM (Phylos, Chorum/Talent, Kappa, EnPulse) oder ICD (Belos, Alto oder GEM) erfolgte eine Zeiterfassung für die Nachsorge der Aggregate (inklusive Erst- und Endabfrage, Testung der Impedanz, Wahrnehmung intrinsischer Signale und Stimulationsreizschwelle). Das Aufsuchen der einzelnen Funktionen am Programmiergerät wurde in den Analysen nicht berücksichtigt. Um eine wirtschaftliche Evaluierung der Ergebnisse zu ermöglichen, wurden die Nachsorgezeiten mit einem fiktiven Referenzkostensatz von 200 Kosteneinheiten pro Aktivitätsstunde bewertet.Die ermittelte Zeit pro Nachsorgevorgang variiert herstellerabhängig bei Einkammer-SM-Aggregaten von 105±11 s (Phylos) bis 125±8 s (Kappa, p>0,05). Bei DDD-SM-Aggregaten wurde eine Nachsorgezeit von 140±25 s (Phylos) bis 282±23 s (Talent, p<0,05) ermittelt. Bei ICD-Aggregaten wurden bei Einkammer-Geräten zwischen 108±5 s (Belos) und 207±21 s (Alto, p<0,05), bei Zweikammer-Aggregaten zwischen 129±8 s (Belos) und 225±23 s (Alto, p<0,05) benötigt. Die unterschiedliche Dauer der Nachsorge beruhte überwiegend auf Problemen in der Telemetrie, Verzögerungen beim Systemstart, bei Erstabfrage und Endabfrage mit Ausdruck sowie der Bestimmung der Wahrnehmung. Durch Einsatz vollautomatischer DDD-SM (EnPulse) ergibt sich eine minimale Nachsorgezeit von 58±3 s. Verglichen mit dem Wert von 282±23 s, p<0,05 beim ungünstigsten SM bedeutet dies eine Verringerung der Nachsorgekosten um nahezu 80%.Der unterschiedliche Einfluss der Gerätetypen verschiedener Hersteller auf die Nachsorgezeit und auf die Wirtschaftlichkeit des Nachsorgeprozesses wird bestätigt. Die Leistungsfähigkeit der Programmiergeräte und die Automatisierung der Gerätetestungen bestimmen dabei die Wirtschaftlichkeit in der Nachsorge von SM/ICD.

[Efficiency potential in the pacemaker/implantable cardioverter defibrillator outpatient clinic].

SummaryThe aim of the present study was to elucidate whether the duration of a technical follow-up (FU) of a pacemaker (PM)/implantable cardioverter defibrillator (ICD) has an impact on cost-effectiveness in the outpatient clinic. We determined the time required for a complete FU of devices from three different manufacturers.In 130 patients (70 VVI/DDD-PM, 60 VVI/DDD-ICD) with either a PM (Phylos, Chorum/Talent, Kappa, EnPulse) or an ICD (Belos, Alto or GEM) the time was recorded for a complete FU including determination of lead impedance, sensing and pacing threshold. The time for activation of individual menue buttons was excluded. On the basis of time required for FU, cost-units (CU) were calculated for 2000 FU/year and for a presumed device longevity (PM 7 years, ICD 5 years).For VVI-PM, the duration of FU was almost identical for devices from different manufacturers (105±11 s to 125±8 s; p=n.s.). However, analysis of DDD-PM revealed marked differences (140±25 s vs 282±23 s, p<0.05). Time for FU of ICDs varied between 108±5 s and 207±21 s (p<0.05) in VVI-ICDs and between 129±8 ms and 225±23 s (p<0.05) in DDD-ICDs. The total savings could be 55 000 CU in VVI- and 53 333 CU in DDD-ICDs. For full automatic DDD-pacemakers (EnPulse) time for FU could be reduced to 58±3 s (p<0.05). Differences in FU times were caused by problems with telemetry, delay during booting of the programmer, interrogation at the beginning and at the end of FU and for sensing tests.Improving not only programmers and devices but also test automaticity could significantly increase cost-efficiency in the outpatient clinic.ZusammenfassungDie vorliegende Studie untersucht geräteabhängige Kostensenkungspotentiale im Prozess der Nachsorge beim Einsatz verschiedener Schrittmacher (SM) und implantierbarer Kardioverter-Defibrillatoren (ICD).Bei 130 Patienten (n=60 VVI-SM/ICD, n=70 DDD-SM/ICD) mit implantiertem SM (Phylos, Chorum/Talent, Kappa, EnPulse) oder ICD (Belos, Alto oder GEM) erfolgte eine Zeiterfassung für die Nachsorge der Aggregate (inklusive Erst- und Endabfrage, Testung der Impedanz, Wahrnehmung intrinsischer Signale und Stimulationsreizschwelle). Das Aufsuchen der einzelnen Funktionen am Programmiergerät wurde in den Analysen nicht berücksichtigt. Um eine wirtschaftliche Evaluierung der Ergebnisse zu ermöglichen, wurden die Nachsorgezeiten mit einem fiktiven Referenzkostensatz von 200 Kosteneinheiten pro Aktivitätsstunde bewertet.Die ermittelte Zeit pro Nachsorgevorgang variiert herstellerabhängig bei Einkammer-SM-Aggregaten von 105±11 s (Phylos) bis 125±8 s (Kappa, p>0,05). Bei DDD-SM-Aggregaten wurde eine Nachsorgezeit von 140±25 s (Phylos) bis 282±23 s (Talent, p<0,05) ermittelt. Bei ICD-Aggregaten wurden bei Einkammer-Geräten zwischen 108±5 s (Belos) und 207±21 s (Alto, p<0,05), bei Zweikammer-Aggregaten zwischen 129±8 s (Belos) und 225±23 s (Alto, p<0,05) benötigt. Die unterschiedliche Dauer der Nachsorge beruhte überwiegend auf Problemen in der Telemetrie, Verzögerungen beim Systemstart, bei Erstabfrage und Endabfrage mit Ausdruck sowie der Bestimmung der Wahrnehmung. Durch Einsatz vollautomatischer DDD-SM (EnPulse) ergibt sich eine minimale Nachsorgezeit von 58±3 s. Verglichen mit dem Wert von 282±23 s, p<0,05 beim ungünstigsten SM bedeutet dies eine Verringerung der Nachsorgekosten um nahezu 80%.Der unterschiedliche Einfluss der Gerätetypen verschiedener Hersteller auf die Nachsorgezeit und auf die Wirtschaftlichkeit des Nachsorgeprozesses wird bestätigt. Die Leistungsfähigkeit der Programmiergeräte und die Automatisierung der Gerätetestungen bestimmen dabei die Wirtschaftlichkeit in der Nachsorge von SM/ICD.