The retrospective observational design limits causal inference and may introduce unmeasured confounding

The gap

Evidence profile

Sourced from the limitations section and limitations and inline gaps of the source papers, classified as general, spanning 3 journals. Those papers have been cited 3 times in total.

Supporting evidence — 3 representative gaps

• Time-Dependent Association of Thoracic Anthropometric Parameters with Survival After In-Hospital Cardiac Arrest: A Retrospective Single-Center Observational Study (2026) · Journal of Clinical Medicine · doi

  the retrospective observational design limits causal inference and may introduce unmeasured confounding - chest CT scans were not systematically obtained in all cardiac arrest patients but rather performed for other clinical indications, potentially introducing selection bias - despite standardized CPR protocols with real-time feedback, actual compression depth may have varied due to rescuer factors, and granular compression data were not available - as a single-center study at a tertiary academic medical center, generalizability to other settings, particularly community hospitals and out-of-hospital cardiac arrests, may be limited

  generallimitations section
  Keywords: retrospective observational design limits causal inference introduce unmeasured
• Risk factors associated with ventricular fibrillation during first ST-elevation myocardial infarction: Individual participant data analysis of 3 prospective case-control studies (2026) · Heart Rhythm · cited 3× · doi

  Even though the 3 studies were all designed specifically to study VF during first STEMI, comprised a large population, and comprehensively phenotyped individuals, our findings should be interpreted considering several limitations, some of which have already been mentioned earlier. Observational studies are always at risk of confounding, and even though we adjusted based on a thorough evaluation of causal pathways, we cannot rule out unmeasured confounding. Only patients who arrived at the hospital and received reperfusion therapy were included in the studies. Thus, some selection bias is pre- sent: patients with VF as their first symptom and/or unwit- nessed cardiac lower probability of resuscitation and survival until hospitalization. As a result, the phenotype of VF cases in this study is not necessarily the same as in all victims to SCD caused by CAD, and results cannot necessarily be extrapolated to populations not included in the study population. arrest have a Patients were interviewed after the event, which increases the risk of recall bias. Patients who have had a cardiac arrest may be more prone to recall SD in their family; however, we believe this risk to be small. After a cardiac arrest, patients may experience retrograde amnesia, or if still comatose, the relatives may be unaware of the immediate circumstances or history. This increases the prevalence of missing data not at random of patients in the case group. Patients using antiar- rhythmic drugs were excluded from the study so results cannot be extrapolated to this subgroup. For example, this might have selected patients with less symptomatic AF, and it is difficult to judge whether results would be the same in in- dividuals receiving, for example, class I or III antiarrhythmic drugs. Finally, the results are vulnerable to misclassification of cases. Postresuscitation ECGs and cardiac enzymes can be difficult to interpret, and deciding whether cardiac arrest judgment. is caused by acute MI demands strong clinical Falsely including cases with a different phenotype, for example, primary arrhythmia or chronic ischemia, could alter the results. Thorough evaluation and adjudication of cases have been done to minimize this effect. Finally, the study is epidemiologic in nature, and further studies are needed to assess genetic, electrical, and mechanistic insights into the ar- rhythmogenesis during acute ischemia.

  generallimitationsevidence 5/5
  Keywords: patients cardiac cases arrest risk cannot example even though population confounding thorough evaluation included bias
• Redefining atherosclerotic cardiovascular disease patients with no standard modifiable risk factors “SMuRF-less”: six rather than four risk factors. Analysis from the Jordan SMuRF-less Study (2026) · Frontiers in Cardiovascular Medicine · doi

  Mortality in STEMI patients without standard modifiable risk factors: a sex- disaggregated analysis of SWEDEHEART registry data. Mortality in patients hospitalised with acute myocardial infarction without standard modifiable risk factors: the ARIC study community surveillance. Higher mortality in acute coronary syndrome patients without standard modifiable risk factors: results from a global meta-analysis of 1,285,722 patients. ST-Segment– Elevation myocardial infarction (STEMI) patients without standard modifiable cardiovascular risk factors—how common are they, and what are their outcomes? J Am Heart Assoc. Prognostic outcomes in acute myocardial infarction patients without standard modifiable risk factors: a multiethnic study of 8,680 Asian patients. Clinical outcomes in patients with ST-segment elevation MI and No standard modifiable cardiovascular risk factors. Patients with STEMI without standard modifiable risk factors.

  generalinline gapsevidence 5/5
  Keywords: patients standard modifiable risk factors without mortality stemi acute myocardial infarction outcomes segment elevation cardiovascular

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