The goal of the this observational study is to gather clinically available data on patients presenting with a suspicion for arrhythmia-induced cardiomyopathy (AiCM) at the University Hospital Basel.

Current studies indicate that AiCM is an under-recognized and an underestimated clinical entity and its prevalence is poorly documented. This project consists of a retrospective longitudinal cohort and case-control study followed by a prospective observational cohort study.

The retrospective pilot study (1200 patients) is to define the incidence of AiCM in patients who presented to the University Hospital of Basel with a reduced left ventricular ejection fraction before or after the diagnosis of an arrhythmia suggestive to lead to an AiCM.

The prospective study part (1500 patients) is to evaluate the predictors of adverse events and re-hospitalizations in patients with a suspicion of AiCM. The diagnosis of AiCM will be established using a "goldstandard diagnosis": 2 independent cardiologists will adjudicate the diagnosis based on all data from the initial hospital stay and follow-up including ECG, laboratory measurements, vital signs, echocardiography, coronary angiography, stress testing and other cardiovascular diagnostic steps. The most likely diagnosis will be chosen among a list of comprehensive, pre-selected choices. In cases of disagreement of the two reviewers, diagnosis will be discussed with a third senior physician and decision made.

In order to optimize the care of patients with AiCM, the researchers intend to determine the prevalence of AICM, evaluate diagnostic criteria that allow an early diagnosis of AICM, and evaluate the current therapeutic management and prognosis of patients with AICM.

Prospective part

Inclusion Criteria:

• Diagnostic or suspicion of AiCM as presence of specified keyword in patient's file or as screened by colleagues of the internal medicine or cardiology clinics
• Signed study consent

Exclusion Criteria:

• Patient's active refusal of the general consent of the University Hospital Basel
• Age <18 years old
• Temporary exclusion criteria: Acute health condition such as myocardial infarction, patients presenting with a major trauma, a sepsis, patients shortly after cardiac surgery, and patients in shock (>100 bpm, <90 systolic BP, evidence of organ dysfunction).
• Life expectancy <1 year (palliative, terminal cancer)

Retrospective part

Inclusion Criteria:

• Patients with a reduced left-ventricular ejection fraction (LVEF ≤50%) or a reduction of 15% in the ejection fraction (EF) between two echocardiographies and a concomitant diagnosis of any arrhythmia likely to lead to AiCM within one year before or after diagnosis of the reduced LVEF from 2010-2021

Exclusion Criteria:

• Age < 18 years old
• Patient's active refusal of the general consent of the University Hospital Basel
• Acute event clearly leading to an acutely reduced LVEF (massive type I myocardial infarction, cardiogenic shock from a coronary or myocardial etiology, septic shock leading to toxic myopathy, hypovolemic shock with reduced EF, cardiac arrest and/or need for resuscitation).
• Patients with life expectancy <1 year (palliative, terminal cancer)

Prospective part (1500 patients):

Patients which have been or currently are in treatment for an AiCM at the University Hospital Basel or who received a new diagnosis/suspicion of such a disease will be included. Patients who have just recovered from an AiCM they presented in the last 10 years will also be enrolled and prospectively followed.

Retrospective part (1200 patients):

Patients with a reduced LVEF (≤50%) or with a reduction of the EF of 15% between two echocardiographies and a concomitant diagnosis of arrhythmia (within one year prior or after the diagnosis of reduced EF) at the University Hospital Basel will be retrospectively identified by conducting a search in the electronic records for keywords of arrhythmia diagnosis and/or reduced EF in several imaging types.