Unveiling Tachycardia-Induced Cardiomyopathy: An Overlooked Medical Phenomenon

CASE: 

We present a 36-year-old woman, BMI 19, with a history of deep vein thrombosis (on Apixaban), rheumatoid arthritis and Crohn’s disease status post previous left hemicolectomy,11 years ago and completion proctocolectomy with end ileostomy ,10 years ago Furthermore, the patient was dependent on total parenteral nutrition given chronic entero-vaginal and enterocutaneous fistulas. The patient was admitted with evidence of a pelvis abscess, surgical intervention was deemed necessary. An exploratory laparotomy with small bowel resection, fistula takedown with an entero-entero anastomosis was performed. The post-operative course was complicated by a pelvic enteric leak, resulting in another exploratory laparotomy, small bowel resection with double barrel jejunostomy. Intra-abdominal wound cultures revealed Vancomycin-Resistant Enterococci and Enterobacter cloacae, hence Meropenem and Daptomycin were initiated. 

Her vital signs revealed persistent tachycardia and hypotension, a transthoracic echocardiography was performed (See Video 1 and Video 2) which revealed moderately decreased LVEF (40%) with regional wall motion abnormalities and a small pericardial effusion. Prior records over the past four months showed a normal left ventricular (LV) ejection fraction (EF) of 60-64% with persistent tachycardia. Cardiology was consulted, the team attributed her LV dysfunction to tachycardia-induced cardiomyopathy given her young age and lack of typical risk factors. 

Video 1: Wall motion abnormalities seen in PSAX view. 

Video 2: Wall motion abnormalities seen in the 4-chamber view

INTRODUCTION:

Tachycardia or Tachyarrhythmia-induced cardiomyopathy (TCMP) is a rare but life-threatening condition that causes LV dysfunction(1, 2). Long-standing tachyarrhythmias can cause non-ischemic dilated cardiomyopathy if left untreated. This condition is potentially reversible if recognized early and managed appropriately(3). Therefore, early diagnosis and management of tachyarrhythmia can significantly impact morbidity, mortality, and prognosis. 

As TCMP is a diagnosis of exclusion, there is limited literature pertaining to the condition, in addition we do not have definitive incidence or prevalence data. Small retrospective case series and individual case report an incidence of 8%–28% in focal/ectopic atrial tachycardias and 9%–34% for ventricular ectopy and non-sustained VT contributing to tachycardia induced cardiomyopathy (4-6). TCMP has been reported to present in weeks, months, or years after the onset of tachyarrhythmia.(4) This review presents a comprehensive update on the definition, pathogenesis, diagnosis, and management of TCMP.

DEFINITION

TCMP is defined as a reversible impairment of ventricular function induced by persistent tachyarrhythmia. The risk of developing TCMP depends on the type and duration of tachycardia. It is also worth noting that it is not only the tachycardia, but also the dyssynchronous myocardial contraction that contributes to LV dysfunction(7).

PATHOPHYSIOLOGY

The development of ventricular dysfunction has been attributed to two mechanisms, firstly it could be induced by a tachyarrhythmia, this entity is known as tachyarrhythmia-induced cardiomyopathy. Secondly, pre-existing ventricular dysfunction can be exacerbated by tachyarrhythmia, this entity is known as tachyarrhythmia mediated cardiomyopathy. Although supraventricular (SVT) arrhythmias, namely atrial fibrillation and atrial flutter with rapid ventricular response are the most common etiology for TCMP, nearly any form of tachyarrhythmia can lead to TCMP(8). Though not common, incessant SVT, paroxysmal atrial tachycardia, persistent atrioventricular reciprocating tachycardia and AV nodal re-entrant tachycardia, sustained sinus tachycardia, frequent ventricular tachycardias, polymorphic ventricular contractions and pacemaker-mediated tachycardia can also lead to TCMP. 

The mechanism of TCMP is not fully defined. The most postulated theory is that chronic tachyarrhythmia leads to abnormalities in energy metabolism, redox stress, calcium overload, calcium mishandling, and diminished beta-adrenergic responsiveness(9). Over time these cellular changes result in the development of cardiac structural changes and subclinical ischemia. Based on animal studies abnormal calcium homeostasis is thought to be responsible for impaired excitation-contraction coupling and diastolic dysfunction. Cardiac remodeling results in LV dilatation, thus leading to an increase in LV wall stress and end-diastolic pressure(10). Ultimately, LV systolic dysfunction ensues.

The progression of these physiological changes leads to a decrease in systemic blood pressure, and increases in LV and pulmonary artery pressures, these changes plateau in one week. Cardiac output, EF, and chamber volumes continue to deteriorate over the following four weeks with the development of symptomatic heart failure (HF) within two to three weeks. TCMP is characterized by both structural and functional myocardial changes.(11)

Based on animal models cessation of tachyarrhythmia results in normalization of right atrial and arterial pressure with significant recovery of LVEF and cardiac output in most cases.(12) Full normalization after 1 to 2 weeks has been reported, however in some cases LVEF may never return to normal. Given the reversibility of TCMP, it is of paramount importance to accurately diagnose and treat the condition in a prompt manner. 

DIAGNOSIS

The classic clinical presentation is symptoms and signs of congestive HF and dilated cardiomyopathy. It should be noted that patients may not necessarily present with arrhythmia, therefore a high index of suspicion needs to be maintained. The main reported symptoms include palpitations, NYHA class III to IV symptoms, and syncope. A small subset of patients are asymptomatic making TCMP a challenging diagnosis. Sudden cardiac death is uncommon, but it has been reported in up to 8% to 12% despite treatment and resolution of tachycardia induced cardiomyopathy(13).

Any patient presenting with heart failure should have a detailed work up to rule out other common etiologies like ischemic, infective, and infiltrative cardiomyopathies. A superimposed TCMP should be considered despite underlying secondary cardiomyopathy (ischemic, infiltrative, or toxic/drug-related) if tachycardia is present.

Holter monitoring or ambulatory ECG monitoring for at least a two-week period is the key to successfully diagnosing TCMP. This length of time is enough to confirm the resting heart rate and underlying rhythm.

Patients may be diagnosed through echocardiography prior to the onset of clinical symptoms or after developing progressive HF. An echocardiogram or cardiac magnetic resonance can assist in identifying structural heart disease and excludes other etiologies. TCMP is characterized by a dilated cardiomyopathy with moderate to severe biventricular systolic dysfunction and normal LV septal and posterior wall thickness.(14)

Neurohormonal markers such as brain natriuretic peptide (BNP) and pro-BNP are commonly elevated depending on the degree of HF and cardiomyopathy. Furthermore, a sudden drop of pro-BNP within a week of elimination of tachycardia is supportive of TCMP.(15)

MANAGEMENT

Restoring sinus rhythm, controlling ventricular rate, and decreasing the burden of ventricular ectopic are the mainstay of treatment, which can all lead to improvement in LV function and symptoms of HF. Concurrently, as with any HF management, the initial treatment of TCMP should include initiation and optimization of medical therapy for HF and LV systolic dysfunction (beta-blockers, angiotensin-converting enzyme inhibitors or angiotensin receptor blockers, diuretic agents, and aldosterone blockers) to optimize reverse remodeling

Restoration of rate and rhythm can be achieved with beta-blockers, calcium channel blockers, antiarrhythmics (AADs), synchronized cardioversion, and/or catheter ablation techniques depending on the type of tachyarrhythmia. In refractory cases, surgical ablation may be warranted. 

Unfortunately, the recovery of TCMP is not always guaranteed. Histopathological abnormalities, diastolic dysfunction, and ventricular dilatation with a hypertrophic response may persist despite normalization of LVEF(16). Therefore, continuous surveillance and follow-up is mandatory.

Arrhythmias leading to tachycardia induced cardiomyopathy and their management strategies: 

CONCLUSION

Appropriate diagnosis and management of TCMP requires a high degree of suspicion given the complexity of presentation of this condition. Timely management of TCMP either in the form of rate control and or rhythm control reverses LV dysfunction in most patients thereby significantly decreasing the morbidity and mortality.

References: 

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