• Full Screen
  • Wide Screen
  • Narrow Screen
  • Increase font size
  • Default font size
  • Decrease font size


Tchavdar Shalganov, Milko Stoyanov, Nikolai Bonev, Joro Nichev
Cardiology Department
National Heart Hospital – Sofia

Address for correspondence:
Assoc. prof. T. Shalganov, MD, PhD
Cardiology Department, National Heart Hospital
65 Koniovitsa Street, 1309 Sofia, Bulgaria
Tel: +359-2-9211-411
Fax: +359-2-9211-402

Summary: We present a patient with congenital long QT syndrome and normal baseline left ventricular function in which several years after the implantation of an automatic cardioverter-defibrillator severe left ventricular dysfunction was found together with a peculiar ECG during antibradycardia pacing. The mechanism for the appearance of the unusual ECG and of the left ventricular dysfunction is discussed.

Key words: antibradycardia pacing; left ventricular dysfunction; LQTS; implantable cardioverter-defibrillator.


The implantation of a cardioverter-defibrillator (ICD) is a method of choice for preventing sudden cardiac death in patients with long QT syndrome (LQTS) which have syncope, cardiac arrest and/or documented polymorphic ventricular tachycardia (VT) or ventricular fibrillation (VF) while treated with beta-blockers. [9, 11] It is presumed that in primary electric cardiac disorders such as LQTS the effective termination of sustained life-threatening ventricular arrhythmias in the absence of structural heart disease or left ventricular (LV) dysfunction may result in normal or near-normal lifespan provided there are not device-related complications.

Case report

We present a 54-year-old female patient with LQTS diagnosed in our institution 4.5 years ago when she had recurrent syncopes while on treatment with propranolol. She had also familial history of LQTS. At the time the diagnosis was made she had normal LV volumes and ejection fraction of 60% on echocardiography, without valvular lesions. One month later a dual-chamber ICD was implanted in another hospital. An atrial lead with active fixation was used. At the same time propranolol was replaced by metoprolol.

Four years after the implantation during routine telemetry check-up delivery of several ICD shocks for polymorphic VT was found. The battery had reached the elective replacement term and was replaced. At this time after the delivered ICD shocks the patient had developed anxiety-depression and sertraline was prescribed. Few months later she complained of progressive fatigue and dyspnea. A diuretic was prescribed and the implanted device was reprogrammed to reduce unnecessary ventricular pacing. This led to reduction of the complaints and to achievement of 100% atrial pacing at a basic rate 90 bpm according to a discharge report. At the beginning of 2015 after having had several new ICD shocks the patient presented for follow-up. During echocardiographic examination severe LV dysfunction with ejection fraction of 33%, mitral regurgitation 2+ and tricuspid regurgitation 2-3+ degree were found. The telemetry found continuous atrial stimulation and 30% ventricular stimulation. However, on the ECG atrial pacing with narrow QRS complex and atrial pacing with wide QRS complex (LBBB-like) was recorded. The patient reported dyspnea during the occurrence of the wide QRS-complexes. A suspicion was raised for the presence of an unrecognized so far accessory pathway causing ventricular preexcitation and worsening LV function. The patient was referred to our institution for electrophysiological study.

At the admission the telemetry showed that the ICD was programmed in DDI pacing mode at a basic rate 95 bpm and AV delay of 105 ms. The antitachycardia mode comprised 2 detection zones: VT detection at a rate above 167 bpm where therapy comprised 2 episodes of antitachycardia pacing (ATP), followed by shocks; VF detection at a rate above 273 bpm where therapy comprised 1 ATP followed by maximum output shocks. Besides, it was found that ventricular pacing during the last monitored period was 70%. It was found as well that the atrial potential sensed by the atrial lead was of very low amplitude, while the ventricular potential recorded by the atrial lead was large (Fig. 1). The electrophysiologic study ruled out an accessory pathway. During the study pacing the posterior right atrium caused a P wave followed by a narrow QRS complex. However, pacing from the implanted atrial lead truly led to a wide QRS complex (Fig. 2). Pacing from the implanted ventricular lead caused the ECG shown on Fig. 3. During the study several episodes of non-syncopal polymorphic VT occurred, lasting up to 12-13 seconds. The treatment was changed – sertraline and metoprolol were substituted with alprazolam and bisoprolol respectively. The basic pacing rate was decreased to 80 bpm, AV delay was increased to 180 ms, detection interval for VT/VF was also increased, VT detection rate was increased to 188 bpm, VF detection rate was decreased to 250 bpm, ATP was programmed ‘off’. The patient was referred back to the implanting hospital for continuation of treatment. The initially programmed parameters were restored there and she was discharged. Only few hours later she felt shock delivery and was admitted to our institution again. At the admission several non-syncopal episodes of polymorphic VT were recorded.

A new reprogramming of the device was done in DDI pacing mode at a rate of 80 bpm and AV delay of 190 ms and 3-day Holter-ECG monitoring was performed. It was found that in 99.5% of the time the heart rhythm was paced and in 68% the paced QRS complex was wide. Eighty percents of the wide QRS complexes were recorded during daytime and only 20% during the night. Different types of recorded ECG and the diurnal variations of the heart rate are shown on Fig. 4. Fluoroscopically the atrial and ventricular leads seemed normally positioned and without pathologic mobility.

What is the mechanism of the occurrence of a wide QRS complex during atrial pacing and what is the cause for the occurrence of severe LV dysfunction in a patient with structurally normal heart?


In this case we faced several problems accumulated over time that went unrecognized.

Firstly, recording an ECG with two different morphologies of the paced QRS from a device with atrial and right ventricular (RV) lead undoubtedly shows a problem. The possible causes are dislocation of the atrial lead, unrecognized implantation of the atrial lead in RV, or RV capture by an atrial stimulus delivered by atrial lead located in close proximity to the tricuspid valve annulus or in the right atrial appendage lying flat on the RV. Dislocation of an active fixation lead implanted more than 4 years before is virtually incredible. Besides, the atrial and far-field ventricular potentials did not show amplitude variations and there was not unusual position or mobility of the atrial lead tip. Unrecognized implantation of the atrial lead in RV can be excluded tooin such a case atrial pacing would cause wide QRS complex all the time, while in our case there were ECG showing paced P wave followed by a narrow QRS complex. However, intermittent RV capture by atrial stimuli is possible and could be explained by a certain body position where the atrial lead would be closer to RV. According to the Holter-ECG data ventricular pacing by the atrial lead prevailed during the day, i.e. probably in an upright body position.

The suspicion for ventricular stimulation effectuated by the atrial lead arised almost immediately and was checked and verified in a manner described by us previously. [1] In brief, in patients in sinus rhythm ventricular stimulation by the ventricular lead causes besides the QRS complex either retrograde P wave clearly visible in at least one ECG lead (Fig. 3) or VA dissociation. However, capture of the ventricular myocardium by an atrial stimulus would induce simultaneously P wave and QRS complex whereupon the P wave would fall entirely within the QRS complex and would not be visible on the ECG. Moreover, the QRS would present different morphology (Fig. 2).

Additional evidence for disadvantageous position of the atrial lead came from the recording of ventricular safety pacing (VSP) (Fig. 4В). VSP is a built-in protective mechanism in dual-chamber devices meant to protect the heart from asystole due to sensing of the atrial stimulus by the ventricular lead and subsequent inhibition of the ventricular stimuluscross-talk inhibition. The activation of VSP is characterized by sudden shortening of the AV interval and immediate subsequent sudden increase of the pacing rate (Fig. 4В и 4С), as in this case. However, in this patient the atrial stimulus was not only sensed by the ventricular lead, but it was able to depolarize the ventricular myocardium and to induce wide QRS complex. Recording of a low-amplitude A-potential and high-amplitude V-potential by the atrial lead also shows close proximity of the lead to the ventricular myocardium.

Ultimately, the reported telemetry data for 100% atrial pacing and 30% ventricular pacing proved to be misleading because the telemetry reports the percentage of the atrial and ventricular pacing based on the number of stimuli delivered by the atrial or the ventricular channel, but cannot discern which chamber is actually paced. In this way all atrial stimuli were reported as atrial pacing without considering the fact that they were actually pacing both the atrium and the ventricle in the majority of time. Combining the ECG data about the QRS morphology and electrical axis during pacing in AAI, VVI and DDI modes with the data of the Holter-ECG monitoring allowed to evaluate precisely the percentage of the ventricular pacing (over 68%) and to demonstrate that it was effectuated almost entirely by the atrial lead. Ventricular pacing by the ventricular lead was recorded in less than 4%, almost entirely in the form of fusion or pseudofusion. It is known that apical RV pacing by a normally positioned ventricular pacing lead induces intra- and interventricular dyssynchrony and is among the main causes for occurrence or aggravation of existing LV dysfunction, increased number of hospital admissions for heart failure, and increased risk of atrial fibrillation in chronically paced patients. [13, 14, 15] It is also known that with dual-chamber devices there is approximately 2.6-fold increase of the risk for occurrence of LV dysfunction if the percentage of ventricular stimulation is beyond 40%. [13] Ventricular pacing by an atrial lead fixed close to the tricuspid valve ring would cause stimulation of the lateral RV and more severe dyssynchrony. In fact, pacing the lateral RV would mimic excitation caused by a manifest right lateral/anterolateral accessory pathway. Data coming from small series and case reports have demonstrated that such a pathway is able to induce severe LV dysfunction. [5, 7] Even with normal atrial lead position a short programmed AV delay (in this case only 105 ms during the first admission to our institution) would preclude the normal AV conduction and would lead to very high percentage of ventricular pacing.

In a wider aspect it is questionable whether the relatively short programmed VT/VF detection time and time to delivery of therapy for non-sustained and non-syncopal polymorphic VT episodes was justified. It is known that ICD shocks, whether appropriate or inappropriate, are associated with increased all-cause mortality, mainly due to heart failure – a phenomenon known as “shock paradox”. [10] This is the reason for the current recommendations for ICD programming to differ from the “standard” programming by the extended detection time and time to therapy delivery. In this way the delivery of therapies for non-sustained VTs that would terminate spontaneously is avoided. This extended time reduces the number of appropriate and inappropriate therapies delivered (ATP and shocks) as well as the all-cause mortality. [6, 8]

Another problem in the case described was the drug therapy with metoprolol and sertraline. The propranolol taken before the ICD implantation was replaced by metoprolol for unknown reasons. Data on the individual efficacy of different beta-blockers are relatively scarce. Nevertheless, it is certain that metoprolol is less effective in preventing events in LQTS patients. [4, 12] The treatment with sertraline started after the first ICD shocks was also inappropriate. The occurrence of anxiety and depression in some patients receiving ICD shocks is well known. This issue was deemed serious enough to be discussed in a recent consensus document. [3] Generally, selective serotonine reuptake inhibitors to which sertraline belongs are suitable for such patients. However, sertraline is included in the list of drugs to be avoided in LQTS patients and was actually contraindicated in our case. [2] On the other hand, alprazolam is not listed in any of the risk categories for TdP provocation and as such is a drug of preference. [2]

After clarifying the actual situation with the ICD functioning, the device was again reprogrammed. The atrial impulse output was reduced while the impulse width was increased. The time to detection and therapy delivery was prolonged. The beta-blocker was changed again, this time with propranolol. A second Holter-ECG demonstrated reduction of the ventricular pacing from over 68% at baseline to less than 32% after reprogramming. Replacement of the atrial lead with a better positioned new one was discussed with the pacing department staff. Finally it was decided to wait for a potential beneficial effect of the changed device settings.

In conclusion, incorrect positioning of an atrial pacing lead can provoke prolonged episodes of RV pacing with subsequent LV dysfunction and heart failure if gone unrecognized. Overreliance only on telemetry follow-up without combination with other ECG monitoring methods can lead to underestimation of an existing problem with serious adverse consequences for the patient’s health.


  1. T. Shalganov, N. Bonev, S. Georgieva, K. Genova. Misrecognition of ventricular tachycardia as supraventricular by a dual-chamber implantable cardioverter-defibrillator – what is the mechanism? – Bulgarian Cardiology, 20, 2014, 1, 43-48.

  2. Available TdP risk categories: Drugs to avoid in congenital long QT. Available on the Internet at Last accessed on May 9, 2015.

  3. Braunschweig, F., G. Boriani, A. Bauer, et al. Management of patients receiving implantable cardiac defibrillator shocks: recommendations for acute and long-term patient management. – Europace, 12, 2010, №12, 1673–1690.

  4. Chockalingam, P., L. Crotti, G. Girardengo, et al. Not all beta-blockers are equal in the management of long QT syndrome types 1 and 2: higher recurrence of events under metoprolol. – J Am Coll Cardiol, 60, 2012, №20, 2092–9.

  5. Dai, C.C., B.J. Guo, W. X. Li, et al. Dyssynchronous ventricular contraction in Wolff-Parkinson-White syndrome: a risk factor for the development of dilated cardiomyopathy. Eur J Pediatr, 172, 2013, №11, 1491-500.

  6. Gasparini, M., A. Proclemer, C. Klersy, et al. Effect of long-detection interval vs standard-detection interval for implantable cardioverter-defibrillators on antitachycardia pacing and shock delivery: the ADVANCE III randomized clinical trial. – JAMA, 309, 2013, №18, 1903-1911.

  7. Ko, J. Left ventricular dysfunction and dilated cardiomyopathy in infants and children with Wolff-Parkinson-White syndrome in the absence of tachyarrhythmias. Korean Circ J, 42, 2012, №12, 803-808.

  8. Moss, A.J., C. Schuger, C. A. Beck, et al. Reduction in inappropriate therapy and mortality through ICD programming. – N Engl J Med, 367, 2012, №24, 2275-83.

  9. Pedersen, C. J., G. Neal Kay, J. Kalman, et al. EHRA/HRS/APHRS Expert consensus on ventricular arrhythmias. – Europace, 16, 2014, №9, 1257-1283.

  10. Poole, J. E., G. W. Johnson, A. S. Hellkamp, et al. Prognostic importance of defibrillator shocks in patients with heart failure. – N Engl J Med, 359, 2008, 10, 1009-17.

  11. Priori, S. G., A. A. Wilde, M. Horie, et al. HRS/EHRA/APHRS Expert consensus statement on the diagnosis and management of patients with inherited primary arrhythmia syndromes. – Heart Rhythm, 10, 2013, №12, 1932-1963.

  12. Schwartz, P.J. Pharmacological and non-pharmacological management of the congenital long QT syndrome: the rationale. – Pharmacol Ther, 131, 2011, №1, 171–177.

  13. Sweeney, M. O., A. S. Hellkamp, K. A. Ellenbogen, et al. Adverse effect of ventricular pacing on heart failure and atrial fibrillation among patients with normal baseline QRS duration in a clinical trial of pacemaker therapy for sinus node dysfunction. – Circulation, 107, 2003, №23, 2932-2937.

  14. Tops, L. F., M. J. Schalij, J. J. Bax. The effects of right ventricular apical pacing on ventricular function and dyssynchrony: implications for therapy. – J Am Coll Cardiol, 54, 2009, 9, 764–76.

  15. Wilcoff, B. L., J. R. Cook, A. E. Epstein, et al. Dual-chamber pacing or ventricular backup pacing in patients with an implantable defibrillator: the Dual Chamber and VVI Implantable Defibrillator. – JAMA, 288, 2002, №24, 3115-3123.

Legends to the figures

Fig. 1. ICD memory recording during atrial pacing with programmed long AV delay. The paced A-potential is barely visible. At the same time the atrial channel senses high-amplitude V-potential. A – atrial channel; V – ventricular channel; AV – sequence and type of events (sensed or paced) recorded by the ICD; FF – far-field ventricular channel.

Fig. 2. ECG during atrial pacing in AAI mode, 90 bpm. The QRS is wide, a P wave is lacking.

Fig. 3. ECG during ventricular pacing (from the third QRS on) in VVI mode, 90 bpm. The QRS is wide, but the morphology and electrical axis are different from those shown on Fig. 2 and a retrograde P wave is clearly visible in at least 6 ECG leads.

Fig. 4. Different types of ECG recorded on a Holter-ECG monitoring. (А) – from the third to the sixth QRSatrial pacing with native AV conduction and QRS complex; 1, 2 and 7 QRSDDD pacing with slight fusion of the paced and the native QRS. The paced AV interval is almost 200 ms. In both pacing modes the pacing rate is 80 bpm. (В) – 1, 2 and 3 QRSDDD pacing at a rate of 80 bpm with partial fusion; 3 to 7 QRSsudden occurrence of a wide QRS during atrial pacing accompanied by sudden increase of the pacing rate to 90 bpm. Inside the wide QRS complexes a second (ventricular) spike is clearly visible with the interval between the two spikes shortening to 100 ms activation of the ventricular safety pacing. (С) – variations of the heart rate during the entire Holter recordinga rate of 90 bpm prevails most of the time, the rate is 80 bpm in significantly less amount of the time, and the transitions between the two pacing rates are sudden due to the activation of ventricular safety pacing.