Understanding Warning Symptoms of Imminent Sudden Cardiac Arrest


Sudden cardiac arrest (SCA) is a life-threatening event that often occurs without prior warning, making it a major concern for public health.

Over the past decade, there has been an increasing interest in identifying warning symptoms that could potentially help predict imminent SCA. In this study, we delve into a comprehensive analysis of warning symptoms preceding out-of-hospital SCA, comparing a dataset from emergency medical services (EMS) electronic health records with a control group reporting similar symptoms but not experiencing SCA.

Our aim is to shed light on the potential utility of warning symptoms in predicting SCA and to identify avenues for future research in this domain.


This study involves a meticulous analysis of a large dataset derived from EMS electronic health records. The dataset encompasses individuals who experienced SCA and those who sought emergency care for other reasons, both groups presenting with prespecified symptoms. The warning symptoms were compared between the SCA group and the control group to discern any associations or patterns.

Symptom Prevalence and Characteristics

The analysis revealed that more than 30% of individuals experiencing SCA reported symptoms of chest pain and dyspnoea. Other symptoms, however, were observed in fewer than 18% of SCA cases. This finding suggests that chest pain and dyspnoea might hold a significant association with impending SCA. Notably, the prevalence of symptoms differed by sex, with chest pain, dyspnoea, and diaphoresis being associated with SCA in men, while dyspnoea alone was linked to SCA among women.

Interestingly, symptoms such as dizziness, abdominal discomfort, weakness, and nausea or vomiting were less common among individuals with SCA when compared to the control group. Moreover, the majority of symptoms occurred as standalone occurrences rather than in combinations, indicating that the presence of a single symptom might warrant attention.

Comparative Studies and Replication

To validate the findings, the study was replicated in an external population with geographical distinctions. The replication yielded consistent results, further emphasizing the robustness of the observed associations between warning symptoms and imminent SCA.

Contextualizing with Previous Research

The study’s results resonate with prior research on symptoms preceding cardiac events. Comparable studies from different countries reported similar symptoms, with dyspnoea, chest pain, and syncope being commonly observed. These congruities strengthen the significance of these symptoms in predicting SCA.

Implications and Future Directions

The study’s findings mark an initial stride in deciphering methods to predict impending SCA. While warning symptoms hold potential as predictive markers, the challenge lies in distinguishing these symptoms from common occurrences. One plausible solution presented is the integration of digital and wireless technologies. A smartphone-based platform could amalgamate various parameters – warning symptoms, demographic data, clinical profile, physiological measurements, and electrocardiogram (ECG) – to formulate a risk score for imminent SCA. However, prospective studies are required to ascertain the effectiveness of warning symptoms in predicting SCA.

Holistic Approach for Enhanced Prediction

Insights from the study advocate for a holistic approach to prediction, combining symptoms with additional attributes for improved accuracy. Such an approach draws from studies on acute coronary syndrome, where symptom characteristics, clinical history, laboratory tests, and ECG findings were collectively more effective in risk stratification.

Sex Differences and Patient Characteristics

Notably, the study highlights sex-based differences in symptom associations with SCA. This aligns with similar findings in acute coronary syndrome studies. The implications underscore the necessity to consider patient demographics and clinical history while predicting SCA based on symptoms.

Limitations and Generalizability

The study acknowledges limitations in terms of reliance on predefined symptom lists and the potential unreliability of symptom reporting during emergencies. Additionally, race and ethnicity data were not extensively available. Hence, the study’s findings might not be universally applicable and need to be interpreted with contextual considerations.

In deep…..


In this chapter, we present the results of our comprehensive study focused on identifying warning symptoms before imminent out-of-hospital sudden cardiac arrest (SCA). We analyze the data obtained from the PRESTO study and its replication in the SUDS population to uncover the associations between symptoms and SCA. The study encompasses a detailed examination of symptom prevalence, sex differences, symptom co-occurrence, and replicability.

Study Population and Data Extraction

In the PRESTO study, a total of 1672 cases of out-of-hospital sudden cardiac arrest of probable cardiac cause were identified from February 1, 2015, to January 31, 2021. Of these, 823 cases (49%) were witnessed by bystanders or EMS personnel. Symptom data were meticulously reviewed in 2021, resulting in 411 participants (50% of 823) with sudden cardiac arrest retained for analysis. The symptom data analysis was compared with a control group of 1171 participants reporting at least one inclusion symptom.

Symptom Prevalence and Characteristics

Among the participants with sudden cardiac arrest, chest pain and dyspnoea emerged as the most prevalent symptoms. Notably, approximately one in ten patients with sudden cardiac arrest reported nausea or vomiting, diaphoresis, seizure-like activity, or weakness. Other symptoms were found in fewer than 6% of sudden cardiac arrest cases. Meanwhile, the control group exhibited distinct symptom profiles, with nausea or vomiting, weakness, dizziness, and abdominal symptoms being more prevalent.

In logistic regression models adjusted for age, sex, and each symptom separately, chest pain, dyspnoea, diaphoresis, and seizure-like activity were significantly associated with higher odds of sudden cardiac arrest. Interaction terms highlighted potential interactions between chest pain and sex, and dyspnoea and sex. No significant interactions were observed for diaphoresis.

Sex Differences and Symptom Associations

Sex-specific analyses unveiled substantial differences in symptom associations. Among men, chest pain, dyspnoea, diaphoresis, and seizure-like activity were significantly more prevalent in sudden cardiac arrest cases. In women, dyspnoea was the sole symptom significantly linked to sudden cardiac arrest. Control participants, irrespective of sex, exhibited consistent symptoms that were more common.

Sex-stratified age-adjusted multivariable models confirmed the associations. In men, chest pain, dyspnoea, and diaphoresis were individually associated with sudden cardiac arrest. Among women, dyspnoea exhibited a significant association, whereas chest pain and diaphoresis did not.

Symptom Co-occurrence

Visual analysis of symptom co-occurrence revealed that most individuals presented with a single symptom noted by EMS, whereas a minority exhibited multiple symptoms. The occurrence of specific symptoms and sets of symptoms varied by age and sex. For instance, among men aged 35–64 years, chest pain often occurred alone, while dyspnoea dominated among men aged 65 years or older. Women aged 35–64 years presented less commonly with the most prevalent symptoms.

Replication and Comparison

The SUDS replication population mirrored many findings from the PRESTO study. Although there were subtle differences, the frequency of individual symptoms, as well as the magnitude and direction of associations between sudden cardiac arrest and controls, were largely similar. The notable exception was that chest pain and diaphoresis did not significantly differ between patients with sudden cardiac arrest and controls in the SUDS replication.

Frequency-Matched Datasets

The consistency of results was reaffirmed in frequency-matched datasets, where case-control comparisons of individual symptoms yielded nearly identical outcomes.

In summary, our comprehensive study delved into the associations between warning symptoms and imminent sudden cardiac arrest. The prevalence of specific symptoms, their sex-specific associations, and symptom co-occurrence were scrutinized in detail. The results underline the complexity of symptom prediction and highlight the need for holistic approaches incorporating multiple factors for enhanced accuracy. This research lays a solid foundation for further prospective studies aimed at refining prediction methodologies and preventing sudden cardiac arrest.


This comprehensive study unravels the complex interplay of warning symptoms and their associations with imminent SCA. While chest pain and dyspnoea stand out as predominant symptoms, their predictive potential is enhanced when integrated with other clinical and biometric factors. The findings encourage the development of novel predictive methodologies that leverage technological advancements. The study’s insights not only bridge existing research gaps but also set the stage for prospective studies that could revolutionize the prediction and prevention of sudden cardiac arrest.


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