Elsevier

Heart Rhythm

Volume 18, Issue 7, July 2021, Pages 1178-1185
Heart Rhythm

Clinical
Sudden Death
Defining idiopathic ventricular fibrillation: A systematic review of diagnostic testing yield in apparently unexplained cardiac arrest

https://doi.org/10.1016/j.hrthm.2021.03.030Get rights and content

Background

Idiopathic ventricular fibrillation (IVF) is diagnosed in patients with apparently unexplained cardiac arrest (UCA) after varying degrees of evaluation. This is largely due to the lack of a standardized approach to UCA.

Objective

We sought to develop an evidence-based diagnostic algorithm for IVF by systematically examining the yield of diagnostic testing in UCA probands.

Methods

Studies reporting the yield of diagnostic testing in UCA were identified in MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, and conference abstracts. Their methodological quality was assessed by the National Institutes of Health quality assessment tool. Meta-analyses were performed using the random effects model.

Results

A total of 21 studies were included. The pooled comprehensive diagnostic testing yield was 43% (95% confidence interval 39%–48%). A lower yield was seen when only definite diagnoses based on the prespecified criteria were used (32% vs 47%; P = .15). Epinephrine challenge, Holter monitoring, and family screening were associated with low yield (<5%), whereas cardiac magnetic resonance imaging, exercise treadmill test, and sodium-channel blocker challenge were associated with high yield (≥5%). Coronary spasm provocation, electrophysiology study, and systematic genetic testing were reported to be abnormal in a high proportion of UCA probands (>10%).

Conclusion

We developed a stepwise algorithm for UCA evaluation and criteria to assess the strength of IVF diagnosis on the basis of the diagnostic yield of UCA testing.

Introduction

Apparently unexplained cardiac arrest (UCA) is diagnosed when patients presenting with cardiac arrest are found to have no obstructive coronary artery disease, normal left ventricular systolic function, and a baseline electrocardiogram that does not identify the cause of cardiac arrest. Finding the cause of UCA is important as it guides family screening and has therapeutic and prognostic implications for probands. Multiple studies have established the role of comprehensive diagnostic testing in revealing a concealed cause of UCA.1, 2, 3, 4, 5, 6 However, these studies used different protocols and reported different results. Consequently, current guidelines recommend performing comprehensive diagnostic testing in UCA probands and only diagnosing idiopathic ventricular fibrillation (IVF) when that fails to identify the cause; however, they do not provide a clear guidance as to the panel of tests that need to be performed for the comprehensive diagnostic testing to be considered complete.7 In addition, some have suggested using certain characteristics to diagnose IVF without the need to exclude other causes. This has resulted in considerable inconsistency in the literature regarding the use of the term IVF to describe UCA probands who underwent some degree of diagnostic testing.7 As such, there is a need to develop a standardized approach to UCA in order to facilitate a uniform diagnosis of IVF in these patients. Thus, we sought to perform a systematic review and meta-analysis of studies reporting the diagnostic testing yield in patients with UCA.

Section snippets

Literature search

The reporting of this review conforms to Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines (see Online Supplemental Table 1 for the PRISMA checklist). A protocol was devised and registered in the International Prospective Register of Systematic Reviews (ID: CRD42020189981). The literature search strategy was developed in consultation with a medical librarian (see Online Supplemental Figure 1 for the complete search strategy). In brief, we searched MEDLINE,

Study selection and characteristics

Our search strategy revealed 3376 citations. Of these, 41 were selected for full-text review. A total of 21 studies met inclusion criteria and were included in the systematic review. Online Supplemental Figure 2 depicts the PRISMA flow diagram. Seven studies reported the yield of comprehensive diagnostic testing and 14 reported the yield of single tests.

Among studies that reported the yield of comprehensive diagnostic testing, 6 were manuscripts and 1 was an abstract. One study reflected the

Discussion

Examining the totality of experience evaluation apparently UCA, the yield of comprehensive diagnostic testing was found to be consistently high. The results of our analysis suggest that a systematic use of CMR, ETT, and SCB should be incorporated in the definition of IVF because of their high yield. More evidence is needed to determine the role of EPS, CSP, and systematic genetic testing.

The significant differences in the conditions diagnosed after comprehensive diagnostic testing of UCA

Conclusion

Based on our systematic review, a comprehensive evaluation of an apparently UCA leads to a diagnosis in 43% of patients. We propose a standardized algorithm for the diagnostic evaluation of UCA, which can serve to assess the strength of an IVF diagnosis. This promises to facilitate a more uniform use of the term IVF in the literature. Given the imperfect features of each test and the corresponding potential for false-positive results, a careful ongoing review of diagnoses made in UCA probands

Acknowledgments

We thank Sarah Visintini, BA, MLIS for her assistance with the systematic search and Margaret Sampson, MLiS, PhD, AHIP for peer reviewing the search strategy.

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    Funding sources: This research did not receive any specific grant from funding agencies in the public, commercial, or non-for-profit sectors.

    Disclosures: The authors have no conflicts of interest to disclose.

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