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............................................................. higher risk of infants born small for their gestational age compared with metoprolol and propranolol, consistent with this association not being a class effect.543,555 Diltiazem has been found to be teratogenic in animals, with only limited human data, and its use is not generally recommended in pregnancy. Verapamil is considered safer than diltiazem and could be used as a second-line drug.153,543

14.2.2 Electrical cardioversion Electrical cardioversion should be the first choice when arrhythmias are haemodynamically unstable. Cardioversion seems safe in all phases of pregnancy as it does not compromise foetal blood flow, and has low risk of inducing foetal arrhythmias or initiating pre-term labour.539 The foetal heart rate should be routinely controlled after cardioversion.

14.2.3 Catheter ablation Catheter ablation should be postponed to the second trimester if possible, but may be necessary in the case of drug-refractory and poorly tolerated tachycardia. It should then be performed at an experienced centre using non-fluoroscopic electroanatomical mapping and catheter navigation systems.556 Catheter ablation of recurrent, drug-refractory AVNRT, AVRT, focal AT, and CTI-dependent atrial flutter has been successful during pregnancy.550552

15 Tachycardia-induced

cardiomyopathy

15.1 Definition

Tachycardia-induced cardiomyopathy (TCM), or more accurately arrhythmia-induced cardiomyopathy, is a reversible cause of impaired LV function due to persistent tachycardia or very frequent ventricular premature beats that can lead to HF and death. The incidence of TCM is unknown but has been reported in all age groups, from foetuses to the elderly.

15.2 Mechanism

The syndrome was initially described with PJRT, but we now know that any chronic cardiac arrhythmia may cause TCM. Incessant AVRTs due to septal APs, rapid AF, idiopathic VT, AT, and persistent ectopic beats are best described.196,233,526,557563 In patients aged <18 years, focal AT is the commonest cause.408 Rapid pacing in animal models induces cytoskeletal changes and remodelling of the extracellular matrix attributed to abnormal calcium cycling, increased catecholamines, decreased beta-1 adrenergic receptor density, oxidative stress, depletion of myocardial energy stores, and myocardial ischaemia due to increased heart rate.559,564 Endomyocardial biopsy specimens from patients with TCM exhibit features distinct from those of other types of cardiomyopathy, including deranged cardiomyocyte and mitochondrial morphology, and macrophage-dominated cardiac inflammation.565 However, it has not been fully established how the majority of patients with frequent premature ventricular contractions have a benign course, whereas <_30% of them may develop cardiomyopathy.566 15.3 Diagnosis

TCM is one of the very few reversible causes of HF and dilated cardiomyopathy, and should be considered in any patient with new onset of LV dysfunction. In the presence of persistent or frequent tachycardia, or frequent premature ventricular contractions, a high index of suspicion should be maintained. The diagnosis is established by excluding other causes of cardiomyopathy, and demonstrating recovery of LV function after eradication of the arrhythmia or control of the ventricular rate. Typically in TCM, LV ejection fraction is <30%, LV end-diastolic diameter is <65 mm, and LV end-systolic diameter is <50 mm.557 More dilated ventricular volumes suggest underlying dilated cardiomyopathy, although some overlapping of the two conditions can occur. In patients with suspected TCM, cardiac magnetic resonance (CMR) is advisable to exclude intrinsic structural change. Serial assessment of N-terminal pro-B-type natriuretic peptide (NTproBNP) and estimation of the ratio of NT-proBNP at baseline to NT-proBNP during follow-up can help differentiate TCM from irreversible idiopathic dilated cardiomyopathy.

15.4 Therapy

In TCM, LV function frequently improves after 3 months of restoration of a normal heart rate. In IST, beta-blockers are indicated. Catheter ablation is indicated when TCM is due to another SVT. When the tachycardia itself cannot be ablated, AV nodal ablation

Recommendations for the therapy of supraventricular tachycardia in patients with suspected or established heart failure due to tachycardiomyopathy

Recommendation Classa Levelb

Catheter ablation is recommended for TCM due to SVT.196,233,418,525 I B Beta-blockers (from the list with proved mortality and morbidity benefits in HFrEF) are recommended for TCM due to SVT, when catheter ablation fails or is not applicable.567 I A It is recommended that TCM is considered in a patient with reduced LV ejection fraction with an elevated heart rate (>100 b.p.m.).557561 I B 24 h (or multiday) ambulatory ECG monitoring should be considered for diagnosis of TCM by identifying subclinical or intermittent arrhythmias.526,557,568 IIa B AV nodal ablation with subsequent pacing (‘ablate and pace’), either biventricular or Hisbundle pacing, is recommended if the tachycardia responsible for the TCM cannot be ablated or controlled by drugs.526,557,564,569572 I C

b.p.m. = beats per minute; ECG = electrocardiogram; HFrEF = heart failure with reduced ejection fraction; LV = left ventricular; SVT = supraventricular tachycardia; TCM = tachycardiomyopathy. aClass of recommendation. bLevel of evidence. Downloaded from academic.oup.com/eurheartj/article/41/5/655/5556821 by guest on 07 October 2026