As their TIC progresses, these animals will have worsening heart function (e.g. : reduced cardiac output and reduced ejection fraction) for 3–5 weeks. The worsened heart function then persists at a stable state until the heart rate is returned to normal. With normal heart rates, these animals begin to demonstrate improving heart function at 1–2 days, and even complete recovery of ejection fraction at 1 month.Human studies of the timecourse of TIC are not as robust as animal studies, though current studies suggest that the majority of people with TIC will recover a significant degree of heart function over months to years. Causes
TIC has been associated with supraventricular tachycardia (SVT), ventricular tachycardia (VT), frequent premature ventricular contractions (PVCs), rapid atrial and ventricular pacing, and left bundle branch block. The types of SVT associated with TIC include atrial fibrillation, atrial flutter, incessant atrial tachycardia, permanent junctional reciprocating tachycardia, atrioventricular reciprocating tachycardia, and atrioventricular nodal reentry tachycardia. Atrial fibrillation is the most common and well-studied etiology of TIC. Diagnosis
There are no specific diagnostic criteria for TIC, and it can be difficult to diagnose for a number of reasons. First, in patients presenting with both tachycardia and cardiomyopathy, it can be difficult to distinguish which is the causative agent. Additionally, it can occur in patients with or without underlying structural heart disease. Previously normal left ventricular ejection fraction or left ventricular systolic dysfunction out of proportion to a patient’s underlying cardiac disease can be important clues to possible TIC.
Additionally, recurrence of the tachyarrhythmia in patients with a history of TIC has been associated with a rapid decline in left ventricular ejection fraction and more severe cardiomyopathy that their prior presentation, which may be a result of the negative cardiac remodeling. There have also been cases of sudden death in patients with a history of TIC, which may be associated with worse baseline left ventricular dysfunction. Given these risks, routine monitoring with clinic visits, ECG, and echocardiography is recommended. Epidemiology
The true incidence of TIC is unclear. Some studies have noted the incidence of TIC in adults with irregular heart rhythms to range from 8% to 34%. Other studies of patients with atrial fibrillation and left ventricular dysfunction estimate that 25–50% of these study participants have some degree of TIC. TIC has been reported in all age groups. See also
Cardiomyopathy
Congestive heart failure

References


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