Looking above the heart: A rare cause of ventricular tachycardia

CASE

A 56-year old man presented with frequent palpitations for 3 months and electrocardiographic evidence of monomorphic ventricular tachycardia (VT). He continued to be symptomatic despite being prescribed anti-arrhythmic medications (propranolol and amiodarone). He did not have any medical comorbidities or significant past medical history. On physical examination he had an enlarged jaw and the soft tissues in his hands and feet appeared swollen (Figure 1A). The rest of his systemic and cardiovascular examination was normal.

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FIGURE 1. (A) Physical examination revealed a prominent lower jaw and swollen soft tissues in the hands suggestive of acromegaly. (B) Twelve-lead ECG morphology was suggestive of a monomorphic ventricular tachycardia with a right bundle branch morphology and inferior axis

The ECG revealed monomorphic VT with a ventricular rate of 150/min. The 12 lead morphology was suggestive of a VT (RBBB inferior axis positive QRS complexes in V1-V6) originating from the anterior mitral annulus (Figure 1B). His baseline echocardiogram revealed concentric left ventricular (LV) hypertrophy (IVSd = 14.2 mm PWd = 12.6) and an LV ejection fraction of 65%. He had frequent premature ventricular complexes (PVCs) with the same QRS morphology and holter monitoring revealed a PVC burden of 52%. Cardiac magnetic resonance imaging (CMRI) and 18-fluorodeoxyglucose positron emission tomography (¹⁸FDG-PET) did not reveal any evidence of late gadolinium enhancement or increased myocardial FDG uptake respectively. Coronary angiography showed normal epicardial coronary arteries.

His plasma growth hormone (GH) (11.2 ng/ml; normal range: 0.03-2.47 ng/ml) and insulin-like growth factor-1 (IGF-1) (622.2 ng/ml; normal range: 81-238 ng/ml) levels were elevated. Serum levels of thyrotropin-stimulating hormone, estradiol, luteinizing hormone, prolactin, and follicle-stimulating hormone were within normal values. Cerebral MRI confirmed the diagnosis of a pituitary adenoma causing acromegaly.

We suspected that the VT was due to acromegaly in this patient. The patient underwent a trans-sphenoidal surgical resection of the pituitary adenoma (Figure 2A,B). Following surgery, there was a serial improvement in his symptoms, PVC burden, and NT-proBNP (Figure 2C). The morphology of the PVCs after surgery was similar to the VT that occurred before surgery (Figure 1B). Repeat echocardiogram at 12 months revealed a regression in LV hypertrophy (IVSd = 11.1 mm PWd = 10.2). At 24 months of post-operative follow-up he remains asymptomatic with no recurrence of VT without any antiarrhythmic medications.

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FIGURE 2. Pathology specimen of the patient's pituitary adenoma showing a typical solid growth pattern with a thin capillary network (100× magnification) (A). High-power micrograph (B) (400×) showing small, monomorphous cells with speckled chromatic, small nucleolus, and moderate amounts of eosinophilic cytoplasm. (C) Serial changes in Insulin-like growth factor 1 (IGF-1) and premature ventricular contraction (PVC) burden following trans-sphenoidal surgery of the pituitary adenoma

DISCUSSION

Although 90% of VTs occur in patients with identifiable heart disease in, 10% of patients there is no evidence of structural abnormalities. Regardless of the etiology, the current guidelines recommend catheter ablation of VT when anti-arrhythmic medications are ineffective or not tolerated by the patient.¹ Idiopathic PVCs and VT can be the presenting manifestation of systemic diseases including acromegaly. A thorough clinical history and physical examination can aid in the diagnosis of systemic diseases that may present with VT.

Associated cardiovascular comorbidities significantly increase the risk of morbidity and all-cause mortality in patients with acromegaly. Cardiac arrhythmias such as supraventricular and ventricular ectopic beats; paroxysmal supraventricular tachycardia atrial fibrillation and bundle branch blocks have been recorded in 40%-50% of acromegalic patients.² Ventricular arrhythmias in these patients are less common and have been reported to strongly related to disease duration and LV mass.

Several studies have attempted to elucidate the pathogenesis of VT in acromegaly. IGF-1 has a dose-dependent positive ionotropic effect with an increase in the intracellular calcium that contributes to early or delayed depolarizations.³ The presence of interstitial fibrosis and myofibrillar derangement can promote arrhythmia by either electrical automaticity or rarely re-entry. Although the data on the role of autonomic dysregulation in acromegaly are controversial it appears that increased heart rate and QT variability contribute to the arrhythmic profile in these patients.⁴

Somatostatin analogs have been found to be effective in reducing the burden of PVCs in patients with acromegaly. Trans-sphenoidal resection of the pituitary adenoma is the preferred and more definitive treatment modality for GH-secreting pituitary adenomas. The use of an implantable cardioverter defibrillator (ICD) in these patients remains controversial.⁵ Baseline LV ejection fraction, probability of recurrenceof life-threatening arrhythmias, and presence of cardiac fibrosis can aid in the clinical decision making of the need for an ICD.

Early diagnosis and initiation of appropriate treatment can lead to a reduction of ventricular arrhythmias and obviate the need of an ICD in patients with VT and acromegaly. In addition, early intervention can prevent serious systemic complications of a GH-secreting pituitary adenoma including diabetes mellitus, systemic hypertension, osteoporosis, and acromegalic cardiomyopathy.

CONFLICT OF INTEREST

The authors do not have any relationships relevant to the contents of this paper to disclose.