TIC is associated with the infiltration of CD68+ macrophages into the myocardium while CD3+ T-cells are very rare. Furthermore, patients with TIC display significant fibrosis due to collagen deposition. The distribution of mitochondria has found to be altered as well, with an enrichment at the intercalated discs (EMID-sign).TIC is likely underdiagnosed due to attribution of the tachyarrhythmia to the cardiomyopathy. Poor control of the tachyarrhythmia can result in worsening of heart failure symptoms and cardiomyopathy. Therefore, it is important to aggressively treat the tachyarrhythmia and monitor patients for resolution of left ventricular systolic dysfunction in cases of suspected TIC. Treatment
Treatment of TIC involves treating both the tachyarrhythmia and the heart failure with the goal of adequate rate control or restoration of the normal heart rhythm (aka. normal sinus rhythm) to reverse the cardiomyopathy. The treatment of the tachyarrhythmia depends on the specific arrhythmia, but possible treatment modalities include rate control, rhythm control with antiarrhythmic agents and cardioversion, radiofrequency (RF) catheter ablation, or AV node ablation with permanent pacemaker implantation.For TIC due to atrial fibrillation, rate control, rhythm control, and RF catheter ablation can be effective to control the tachyarrhythmia and improve left ventricular systolic function. For TIC due to atrial flutter, rate control is often difficult to achieve, and RF catheter ablation has a relatively high success rate with a low risk of complications. In patients with TIC due to other types of SVT, RF catheter ablation is recommended as a first-line treatment.
In patients with TIC due to VT or PVCs, both antiarrhythmics and RF catheter ablation can be used. However, the options for antiarrhythmic agents are limited because certain agents can be proarrhythmic in the setting of myocardial dysfunction in TIC. Therefore, RF catheter ablation is often a safe and effective choice for treatment VT and PVCs causing TIC. In cases where other treatment strategies fail, AV node ablation with permanent pacemaker implantation can also be used to treat the tachyarrhythmia.The treatment of heart failure commonly involves neurohormonal blockade with beta-blockers and angiotensin convertase inhibitors (ACEIs) or angiotensin II receptor blockers (ARBs) along with symptomatic management with diuretics. Beta-blockers and ACE inhibitors can inhibit and potentially reverse the negative cardiac remodeling, which refers to structural changes in the heart, that occurs in TIC. However, the need to continue these agents after treatment of the tacharrhythmia and resolution of left ventricular systolic dysfunction remains controversial. Prognosis
The prognosis for TIC after treatment of the underlying tachyarrhythmia is generally good. Studies show that left ventricular function often improves within 1 month of treatment of the tachyarrhythmia, and normalization of the left ventricular ejection fraction occurs in the majority of patients by 3 to 4 months. In some patients however, recovery of this function can take greater than 1 year or be incomplete. In addition, despite improvement in the left ventricular ejection fraction, studies have demonstrated that patients with prior TIC continue to demonstrate signs of negative cardiac remodeling including increased left ventricular end-systolic dimension, end-systolic volume, and end-diastolic volume.