Table 2.

National Hearts in Rhythm Organization (HiRO) Registry criteria for assigning working diagnosis

	Strength = Definite	Strength = Probable	Strength = Possible
LQTS7	LQTS risk score ≥ 3.5 in the absence of a secondary cause for QT prolongation and/or Unequivocally pathogenic variant in one of the LQTS genes and/or QTc ≥ 500 ms in repeated 12-lead electrocardiogram (ECG) in the absence of a secondary cause for QT prolongation	QTc between 480 and 499 ms in repeated 12-lead ECGs in a patient with unexplained syncope in the absence of a secondary cause for QT prolongation and in the absence of a pathogenic variant	LQTS risk score 2.0-3.5 in the presence of a family history of definite LQTS that is genotype negative or when genetic testing has not been performed
Acquired LQTS (aLQTS)	LQTS risk score ≥ 3.5 in the presence of a secondary cause of QT prolongation and/or QTc ≥ 500 ms in the presence of a secondary cause of QT prolongation	QTc between 480 and 499 ms in a patient with unexplained syncope in the presence of a secondary cause of QT prolongation	NA
BrS7	ST elevation with type 1 morphology ≥ 2 mm in ≥ 1 of the right precordial leads V1-V2 positioned in the 4th, 3rd, or 2nd intercostal spaces, either spontaneously or after provocative drug test with IV class 1 drugs	Unequivocal pathogenic variant in SCN5A leading to decreased Nav1.5 function in the presence of family history of definite BrS or in the context of a molecular autopsy	ST elevation with type 2 morphology and provocative testing has not been performed in presence of family history of definite BrS
CPVT7	Structurally normal heart, normal ECG, and unexplained exercise or catecholamine-induced bidirectional VT or PVCs or VT in an individual younger than 40 y and/or Presence of an unequivocal pathogenic variant and/or Family members of a CPVT index case with a normal heart who manifest exercise-induced premature ventricular contractions or bidirectional/polymorphic VT	Structurally normal heart, normal ECG, and unexplained exercise or catecholamine-induced bidirectional VT or PVCs) or VT in an individual older than 40 y	NA
SQTS7	QTc < 330 ms	QTc < 360 ms and one or more of: 1.pathogenic variant 2.family history of SQTS 3.family history of sudden death < 40 y 4.Survival of VT/VF in the absence of heart disease	Unequivocal pathogenic variant carrier with a QTc ≥ 360 ms
ERS7	J-point elevation ≥ 1 mm in ≥ 2 contiguous inferior and/or lateral leads of a 12-lead in a patient resuscitated from otherwise unexplained VF or polymorphic VT	SCD victim with a negative autopsy and medical chart review, with a previous ECG demonstrating J-point elevation ≥ 1 mm in ≥ 2 contiguous inferior and/or lateral leads of a standard 12-lead ECG	NA
SCVF (Steinberg)	Short-coupled PVCs (RR < 350 ms) triggering polymorphic VT/VF, where other known electrical and myocardial diseases have been excluded	Resuscitated ventricular fibrillation and documented recurrent short-coupled PVCs (< 350 ms) without demonstration of PVC-triggered VT/VF, where other known electrical and myocardial diseases have been excluded	NA
UCA/IVF7,20,21	Resuscitated cardiac arrest from a shockable rhythm, where known etiologies have been excluded, using cardiac imaging, stress/epinephrine, and procainamide testing	Resuscitated cardiac arrest from a shockable rhythm, where known etiologies have been partially excluded	NA
SADS	Sudden cardiac death with negative toxicology and normal autopsy including cardiac pathology expertise, not otherwise fulfilling diagnostic criteria of specific syndromes	Sudden cardiac death with negative toxicology and normal autopsy without cardiac pathology expertise or with nondiagnostic cardiac abnormalities, not otherwise fulfilling diagnostic criteria of specific syndromes	Sudden cardiac death below age 40 in an otherwise healthy individual with incomplete postmortem assessment (autopsy and toxicology)
Polymorphic VT	Syncope with documented polymorphic VT without cardiac arrest, where known etiologies have been excluded	NA	NA
HCM22	Wall thickness ≥ 15 mm (z-score ≥ 2 in children) in 1 or more LV myocardial segments that is not explained solely by loading conditions (eg, SBP > 160), excluding isolated basal septal hypertrophy in the elderly and/or Wall thickness ≥ 13 mm in first-degree relatives of patients with definite HCM or with a pathogenic variant	NA	Wall thickness 13-14 mm in one or more LV myocardial segments that is not explained solely by loading conditions (eg, SBP > 160), excluding isolated basal septal hypertrophy in the elderly, in the absence of first-degree relatives of patients with definite HCM
DCM	LV systolic dysfunction (LVEF < 50%) AND enlargement, that is not explained by abnormal loading conditions, coronary artery disease, or a recent cardiac arrest	NA	NA
ARVC23	Task Force criteria: 2 major or 1 major and 2 minor criteria or 4 minor from different categories	Task Force criteria: 1 major and 1 minor or 3 minor criteria from different categories	Task Force criteria: 1 major or 2 minor criteria from different categories
LVNC	LVNC diagnosed by TTE or CMR	NA	NA
UCM	Unclassified cardiomyopathy: presence of cardiomyopathy not fulfilling diagnostic criteria for the 4 other entities, eg, presence of significant fibrosis on magnetic resonance. Describe clinical findings in comments	UCA/SCD with a pathogenic or likely pathogenic variant in a cardiomyopathy gene but no cardiomyopathy phenotype	NA
Myocarditis24,25	Endomyocardial biopsy-confirmed myocarditis (Dallas criteria)	Clinically suspected myocarditis according to published criteria including CMR evidence, in the absence of an endomyocardial biopsy	Clinically suspected myocarditis according to published criteria in the absence of cardiac magnetic resonance imaging and endomyocardial biopsy
Coronary spasm26	Evidence of angina in the absence of fixed coronary artery stenosis > 50% AND Transient ischemic ECG changes during the spontaneous episodes and/or a positive acetylcholine/ergonovine test showing evidence of > 90% coronary vasoconstriction	Polymorphic VT/VF in the absence of fixed coronary artery stenosis > 50% or another etiology AND a positive acetylcholine/ergonovine test showing evidence of > 90% coronary vasoconstriction	Evidence of nitrate-responsive angina in the absence of transient ischaemic ECG changes and coronary artery spasm
Malignant mitral valve prolapse syndrome27	Presence of bileaflet mitral valve prolapse in a patient with otherwise unexplained polymorphic VT/VF with frequent complex PVCs thought to originate from the papillary muscle	Presence of bileaflet mitral valve prolapse in a patient with otherwise unexplained polymorphic VT/VF in the absence of frequent PVCs originating from the papillary muscle OR Presence of single leaflet mitral valve prolapse in a patient with otherwise unexplained polymorphic VT/VF and evidence of myocardial fibrosis	Presence of single leaflet mitral valve prolapse in a patient with otherwise unexplained polymorphic VT/VF, without myocardial fibrosis or without assessment for myocardial fibrosis
Pause-dependent VT/VF	Polymorphic VT/VF in the context of severe bradycardia with recurrent documented PVCs/VT after pauses	NA	NA
Unaffected/normal	Family member negative for known familial mutation with normal cardiac investigations	Family member with normal cardiac investigations where genetic testing is negative in proband or unavailable OR Family member negative for known familial mutation with borderline cardiac investigations not otherwise fulfilling diagnostic criteria	NA
Unclassified genetic variant carrier	Phenotypically unaffected carrier of a pathogenic or likely pathogenic variant not otherwise fitting other diagnostic criteria	Phenotypically unaffected carrier of a variant(s) of unknown significance not otherwise fitting other diagnostic criteria	NA

ARVC, arrhythmogenic right ventricular cardiomyopathy; BrS, Brugada syndrome; CMR, cardiovascular magnetic resonance imaging; CPVT, catecholaminergic polymorphic ventricular tachycardia; DCM, dilated cardiomyopathy; ERS, early repolarization syndrome; HCM, hypertrophic cardiomyopathy; IV, intravenous; IVF, idiopathic ventricular fibrillation; LQTS, long QT syndrome; LVEF, left ventricular ejection fraction; LVNC, left ventricular noncompaction; PVC, premature ventricular contraction; SADS, sudden arrhythmogenic death syndrome; SBP, systemic blood pressure; SCD, sudden cardiac death; SCVF, short coupled ventricular fibrillation; SQTS, short QT syndrome; TTE, transthoracic echocardiogram; UCA, unexplained cardiac arrest; UCM, unclassified cardiomyopathy; VF, ventricular fibrillation; VT, ventricular tachycardia.