Author + information
- Received May 14, 2018
- Revision received May 27, 2018
- Accepted May 31, 2018
- Published online October 15, 2018.
- aCardiothoracic Department, Manzoni Hospital, Lecco, Italy
- bArrhythmia and Electrophysiology Research Center, Istituto di Ricovero e Cura a Carattere Scientifico Humanitas Research and University Hospital, Rozzano (Milan), Italy
- ↵∗Address for correspondence:
Dr. Gianluca Epicoco, Cardiothoracic Department, Manzoni Hospital, Via dell’eremo 9, 23900 Lecco, Italy.
A 30-year-old man, known for ventricular pre-excitation and recurrent episodes of typical atrial flutter (Figures 1A and 1B), was referred to our center. Notably, his father was affected by hypertrophic cardiomyopathy and received a permanent pacemaker for complete atrioventricular (AV) block at 35 years of age. On admission, the basal 12-lead electrocardiogram showed sinus rhythm with a manifest pre-excitation pattern, compatible with an anteroseptal accessory pathway (AP). Electrocardiographic features included a shortened PR interval (100 ms), a markedly broad QRS interval (160 ms), and high voltages (P and QRS), indicating associated diffuse hypertrophy (Figure 1A). Echocardiogram (Figures 1C and 1D) and cardiac magnetic resonance imaging (Figure 1E) showed marked and symmetric hypertrophic cardiomyopathy without outflow obstruction (maximal wall thickness: 28 mm).
An electrophysiological study was performed and multipolar diagnostic catheters were placed via the femoral veins. Despite careful right-side mapping, a discrete His potential could not be clearly identified during the procedure. Programmed atrial stimulation showed decremental antegrade conduction over the AP (Figure 1F) with a fixed pre-excitation degree. Furthermore, no change in pre-excitation degree was observed during multisite atrial pacing from right atrium and distal coronary sinus (Figure 1G). Intriguingly, a sinus P wave was blocked without any conduction over the AP or the AV node (Figure 1H). Moreover, spontaneous junctional beats were observed to produce an identical pre-excitation morphology (Figure 1I), suggesting an infra-atrial AP. However, these apparently pre-excited junctional beats could also represent spontaneous firing from the AP itself. Because the pre-excitation degree was not typical for a fasciculoventricular tract, the aforementioned electrophysiological features are likely to be associated with a single AV connection (i.e., AP connection without intrinsic AV nodal conduction) or an infra-atrial AP (e.g., nodoventricular). No AV re-entrant tachycardia was inducible despite aggressive stimulation protocols and isoproterenol infusion. Considering the bystander nature of this AP, catheter ablation of the cavotricuspid isthmus was only performed.
Subsequent genetic testing identified a missense mutation (His530Arg substitution) in the protein kinase, adenosine monophosphate–activated, noncatalytic, gamma-2 (PRKAG2) gene. During the follow-up, the patient remained asymptomatic with no tachyarrhythmia recurrence, but he underwent a dual-chamber implantable cardioverter-defibrillator insertion for paroxysmal AV block and primary prevention of sudden cardiac death. This case highlights that atypical pre-excitation variants may occur in the context of nonsarcomeric hypertrophic cardiomyopathy. The coexistence of ventricular hypertrophy, ventricular pre-excitation, atrial arrhythmias, and conduction disturbances should raise the suspicion of rare inherited conditions such as the PRKAG2 syndrome (1).
The authors have reported that they have no relationships relevant to the contents of this paper to disclose.
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- Received May 14, 2018.
- Revision received May 27, 2018.
- Accepted May 31, 2018.
- 2018 American College of Cardiology Foundation