Fast monomorphic ventricular tachycardia (≥188 beats/min) in non-ischemic cardiomyopathies was successfully terminated by antitachycardia pacing across five distinct arrhythmogenic substrates, illustrating that 'ventricular rate is an imperfect surrogate for ATP susceptibility and should not alone dictate device-programming strategy.'
Key Findings
Results
Antitachycardia pacing (ATP) successfully terminated fast sustained monomorphic VT at rates ≥188 beats/min across five patients with distinct non-ischemic cardiomyopathies.
All five patients had fast sustained monomorphic VT with tachycardia cycle length ≤320 ms (≥188 beats/min)
Some episodes fell in the very fast/VF-zone at rates >250 beats/min
Substrates included LMNA cardiomyopathy, TTN truncating variant-associated dilated cardiomyopathy, δ-sarcoglycan-associated dilated cardiomyopathy, severe non-ischemic cardiomyopathy with CRT-D, and hypertrophic cardiomyopathy with apical LV aneurysm
ATP terminated episodes without high-energy shock delivery across all five heterogeneous substrates
Results
A patient with TTN truncating variant-associated dilated cardiomyopathy experienced VT at approximately 260 beats/min that was successfully terminated by ATP.
VT rate of approximately 260 beats/min falls well within the conventionally defined VF zone (>250 beats/min)
ATP termination was achieved without shock delivery
This case illustrates ATP susceptibility even at very rapid rates in non-ischemic dilated cardiomyopathy
Results
A patient with severe non-ischemic cardiomyopathy, left bundle branch block, and CRT-D implantation experienced 27 early post-implant VT episodes, all terminated by ATP.
All 27 VT episodes were terminated successfully by ATP
The substrate included circumferential ring-like fibrosis
No shock delivery was required for any of the 27 episodes
This case demonstrates high-volume ATP efficacy in the early post-implant period
Results
A patient with hypertrophic cardiomyopathy complicated by an apical left ventricular aneurysm and diffuse late gadolinium enhancement experienced shock-free electrical storm managed with ATP.
The patient had diffuse late gadolinium enhancement on cardiac MRI
Electrical storm was managed without shock delivery using ATP
This represents ATP efficacy in a complex substrate with extensive fibrosis
Results
A patient with δ-sarcoglycan-associated dilated cardiomyopathy experienced clustered VT/electrical storm that was terminated by ATP.
The substrate involved δ-sarcoglycan gene variant-associated dilated cardiomyopathy
Clustered VT meeting criteria for electrical storm was successfully managed with ATP
No high-energy shock delivery was required
Results
Several VT episodes across the case series were asymptomatic or initially attributed to atrial arrhythmia, with device interrogation ultimately documenting sustained VT requiring therapy.
Asymptomatic episodes underscore the importance of device monitoring and interrogation
Some episodes were initially misattributed to atrial arrhythmia before device interrogation confirmed sustained VT
This highlights that fast VT in non-ischemic cardiomyopathy may not always present with typical symptoms
Discussion
The authors identify the unifying electrophysiological phenotype across all five cases as fast, regular, monomorphic VT sustained by an organized reentrant circuit with an accessible excitable gap.
Tachycardia regularity and monomorphic morphology were consistent across all five heterogeneous substrates
An organized reentrant circuit with an accessible excitable gap was cited as the mechanism enabling ATP susceptibility
ATP response was described as reflecting 'the interaction among circuit organization, scar architecture, tachycardia cycle length, pacing-vector access, detection-zone design, and ATP programming'
Conclusions
The authors conclude that ventricular rate alone should not dictate ICD programming strategy, and fast VT in non-ischemic cardiomyopathy should not be considered intrinsically shock-dependent.
The paper states: 'ventricular rate, although relevant to risk assessment and therapy, is an imperfect surrogate for ATP susceptibility and should not alone dictate device-programming strategy'
The findings are described as complementing randomized trial evidence from PainFREE Rx II, PITAGORA ICD, MADIT-RIT, ADVANCE III, and APPRAISE ATP trials
The authors advocate for shock-minimizing ICD programming when VT is sustained, regular, and monomorphic, preserving defibrillation as back-up therapy
What This Means
This research presents five patients with different types of non-ischemic heart muscle diseases (cardiomyopathies caused by genetic or structural abnormalities rather than blocked coronary arteries) who experienced dangerously fast abnormal heart rhythms called ventricular tachycardia (VT). In each case, the implanted defibrillator device was able to stop the fast rhythm using a technique called antitachycardia pacing (ATP) — where the device delivers a burst of rapid, low-energy electrical pulses to interrupt and reset the abnormal rhythm — rather than resorting to a painful high-energy shock. Notably, some of these episodes exceeded 250 beats per minute, a rate traditionally considered to require immediate shock treatment.
This research suggests that the rate of a fast heart rhythm alone is not a reliable indicator of whether a painful shock is necessary. What matters more is whether the rhythm is organized, regular, and sustained by a predictable electrical circuit — qualities that make it susceptible to being 'outpaced' by ATP. The authors found this pattern across five very different underlying heart conditions, including genetic cardiomyopathies caused by variants in the LMNA, TTN, and δ-sarcoglycan genes, as well as hypertrophic cardiomyopathy with scarring. Some episodes were initially mistaken for less dangerous atrial arrhythmias or caused no symptoms at all, only being identified through device data review.
The practical implication of this research is that implantable defibrillators in patients with non-ischemic cardiomyopathies may be programmed to attempt ATP before delivering shocks, even for very fast rhythms, provided the rhythm has the right characteristics. This could spare patients the pain, psychological distress, and potential harm associated with unnecessary shocks. The findings add real-world support to several large clinical trials that have already demonstrated benefits of shock-minimizing device programming strategies.
Karakasis P, Stavropoulos G, Efthimiadis G, Karamitsos T, Fragakis N. (2026). Antitachycardia Pacing for Fast Scar-Mediated Ventricular Tachycardia Across Non-Ischemic Cardiomyopathies: A Case Series.. International medical case reports journal. https://doi.org/10.2147/IMCRJ.S629503