The diagnosis of TIC is made after excluding other causes of cardiomyopathy and observing resolution of the left ventricular systolic dysfunction with treatment of the tachycardia.Specific tests that can be used in the diagnosis and monitoring of TIC include:
electrocardiography (EKG)
Continuous cardiac rhythm monitoring (e.g. Holter monitor)
echocardiography
Radionuclide imaging
Endomyocardial biopsy
Cardiac magnetic resonance imaging (CMR)
N-terminal pro-B-type natriuretic peptide (NT-pro BNP)Cardiac rhythm monitors can be used to diagnose tachyarrhythmias. The most common modality used is an EKG. A continuous rhythm monitor such as a Holter monitor can be used to characterize the frequency of a tachyarrhythmia over a longer period of time. Additionally, some patients may not present to the clinical setting in an abnormal rhythm, and continuous rhythm monitor can be useful to determine if an arrhythmia is present over a longer duration of time.To assess cardiac structure and function, echocardiography is the most commonly available and utilized modality. In addition to decreased left ventricular ejection fraction, studies indicate that patients with TIC may have a smaller left ventricular end-diastolic dimension compared to patients with idiopathic dilated cardiomyopathy. Radionuclide imaging can be used as a non-invasive test to detect myocardial ischemia. Cardiac MRI has also been used to evaluate patients with possible TIC. Late-gadolinium enhancement on cardiac MRI indicates the presence of fibrosis and scarring, and may be evidence of cardiomyopathy not due to tachycardia. A decline in serial NT-pro BNP with control of tachyarrhythmia indicates reversibility of the cardiomyopathy, which would also suggest TIC.People with TIC display distinct changes in endomyocardial biopsies.
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.