European Journal of Cardiovascular Medicine

Dengue fever, a mosquito-borne viral illness, continues to pose a substantial global health burden, with over 5 million reported cases and around 5,000 deaths in 2023 alone [1]. Although the majority of cases are asymptomatic or mild, a small but critical fraction progress to severe dengue, characterized by complications such as plasma leakage, hemorrhage, and organ impairment [2,3]. The 2009 WHO guidelines and recent CDC classifications define dengue with warning signs—including abdominal pain, persistent vomiting, clinical fluid accumulation, mucosal bleeding, lethargy/restlessness, liver enlargement, rising hematocrit, and thrombocytopenia—as indicative of increased risk for deterioration [4,5].

Historically, cardiac involvement in dengue has not been the primary clinical focus. However, emerging evidence highlights that dengue can induce a variety of cardiac manifestations. ECG changes are among the most frequent, ranging from benign sinus bradycardia to conduction blocks, arrhythmias, and even myocarditis in rare instances [6–8]. In a literature review, Parchani et al. noted that conduction abnormalities are typically transient and resolve within three weeks in most patients [6]. Myocardial inflammation and arrhythmias can occur, and in severe cases, fulminant myocarditis has been observed in up to 13% of patients [7].

Several case reports further underscore atypical cardiac presentations. For example, Cristodulo et al. described a dengue patient with myocardial and pericardial involvement, resolved with anti-inflammatory treatment [8]. More recently, Siregar et al. reported a case in 2025 where a transient left bundle branch block (LBBB) in dengue masqueraded as ischemic T-wave inversion—termed “cardiac memory”—highlighting diagnostic challenges in interpreting ECG changes in this context [9]. Moreover, de Gaay Fortman et al. reported perimyocarditis in dengue shock syndrome, emphasizing that cardiac injury, although rare, can be life-threatening, especially in severe dengue presentations [10].

Despite this growing awareness, data correlating ECG abnormalities with warning signs of dengue remain limited. A focused study (IJAM) observed that the most common cardiac manifestation was transient rhythm disturbance—particularly sinus bradycardia—and found significant correlations between cardiac manifestations and most warning signs (except lethargy/restlessness and hepatomegaly) [11]. Identifying such associations is clinically valuable, as early detection of ECG changes could prompt timely interventions before hemodynamic compromise.

Accordingly, your study titled “To study cardiac manifestations in patients presenting with dengue infection and to find out the correlation of cardiac manifestations to warning signs of dengue” aims to observe ECG changes in dengue patients and explore their correlation with recognized warning signs. This could enhance our understanding of the cardiac dimension of dengue and support better clinical monitoring and risk stratificationa

This hospital-based observational study was conducted in the Department of Medicine at a tertiary care hospital over a defined period after obtaining institutional ethical clearance. A total of 120 patients clinically diagnosed with dengue infection were included in the study. The diagnosis of dengue was established using NS1 antigen detection and/or IgM antibody positivity through ELISA testing, supported by clinical features consistent with dengue fever. Patients of all age groups above 18 years who were admitted with laboratory-confirmed dengue infection were eligible for inclusion. Patients with pre-existing cardiac diseases such as ischemic heart disease, valvular heart disease, congenital heart disease, or those on medications affecting cardiac conduction were excluded to avoid confounding factors.

Detailed demographic and clinical information, including age, gender, presenting symptoms, and presence of warning signs, was recorded using a predesigned proforma. Warning signs were defined in accordance with WHO 2009 guidelines and included abdominal pain, persistent vomiting, mucosal bleeding, hepatomegaly, lethargy/restlessness, clinical fluid accumulation, and a rapid fall in platelet count associated with rising hematocrit. Baseline hematological and biochemical investigations were performed, including complete blood counts, liver function tests, and renal function tests, to support clinical categorization.

Electrocardiographic evaluation was performed in all 120 patients at admission and repeated during the course of hospitalization if the patient developed warning signs or clinical deterioration. Standard 12-lead ECGs were obtained and interpreted by a qualified physician, with particular attention given to rhythm disturbances, conduction abnormalities, ST-T wave changes, and any evidence suggestive of myocarditis or ischemic patterns. Findings were recorded systematically and correlated with the clinical course of dengue illness and the presence of warning signs.

Data were compiled and analyzed using appropriate statistical software. Continuous variables such as age were expressed as mean ± standard deviation, while categorical variables such as gender distribution, warning signs, and ECG abnormalities were expressed as frequencies and percentages. The chi-square test was used to assess associations between categorical variables, while Student’s t-test was applied for continuous variables wherever applicable. Correlation of ECG changes with warning signs of dengue was evaluated using Pearson’s correlation coefficient. A p-value of less than 0.05 was considered statistically significant.

Table 1 shows the baseline clinical characteristics of the 120 dengue patients included in the study. The majority of patients were between 31–46 years (n=54), followed by 15–30 years (n=35) and 45–60 years (n=31). A male predominance was observed with 76 males compared to 44 females, reflecting the higher exposure and susceptibility of males in this cohort. These findings suggest that dengue infection in this study was more prevalent among young and middle-aged adults, with a male preponderance.

Table 2 depicts the distribution of warning signs among the 120 dengue patients. Abdominal pain (n=60) and persistent vomiting (n=54) were the most frequently observed warning signs, followed by lethargy/restlessness (n=36), shock (n=30), and acute respiratory distress syndrome (ARDS) in 30 cases. Clinical fluid accumulation was seen in 30 patients, mucosal bleeding in 24 patients, while hepatomegaly >2 cm was present in 15 cases. These findings emphasize that gastrointestinal and systemic warning signs were predominant in this cohort, indicating their importance in early clinical recognition of potential complications.

Table 3 outlines the electrocardiographic (ECG) changes in patients with dengue infection. The most common abnormality observed was sinus bradycardia (n=72), followed by sinus tachycardia (n=33) and ventricular ectopics (n=18). First degree heart block was observed in 13 patients, while only 16 patients maintained a normal sinus rhythm throughout their illness. These findings highlight the predominance of rhythm disturbances, particularly bradyarrhythmias, as the major cardiac manifestations in dengue patients.

Table 4 shows the correlation of warning signs to ECG abnormalities. Significant associations were noted between abdominal pain, mucosal bleed, fluid accumulation, shock, respiratory distress, and ARDS with the presence of ECG abnormalities. For instance, abdominal pain was significantly associated with ECG changes (p=0.041), while mucosal bleed (p=0.028), fluid accumulation (p=0.031), shock (p=0.014), respiratory distress (p=0.022), and ARDS (p=0.009) also demonstrated strong correlations. In contrast, persistent vomiting (p=0.650), lethargy/restlessness (p=0.182), and hepatomegaly (p=0.774) did not show statistically significant associations. These results suggest that while some warning signs strongly predict cardiac involvement, others do not consistently correlate with ECG abnormalities.

Table 1: Baseline clinical characteristics of dengue patients (n=120)

Table 2: Warning signs of dengue (n=120)

Table 3: Electrocardiographic (ECG) changes in dengue patients (n=120)

Table 4: Correlation of warning signs to ECG abnormality (n=120)

The present study highlights the spectrum of cardiac manifestations in patients with dengue infection and emphasizes the correlation of electrocardiographic abnormalities with dengue warning signs. Among the 120 patients studied, rhythm disturbances were the most prominent findings, particularly sinus bradycardia, which is consistent with the increasing body of literature demonstrating bradyarrhythmias as a hallmark of dengue-associated cardiac involvement. Recent research indicates that ECG abnormalities in dengue are multifactorial, with direct viral invasion, cytokine-mediated myocardial injury, electrolyte imbalances, and autonomic dysfunction all contributing to transient but clinically significant changes [11].

In the context of warning signs, our results demonstrated statistically significant associations between abdominal pain, mucosal bleeding, fluid accumulation, shock, respiratory distress, and ARDS with ECG abnormalities. These findings suggest that the presence of systemic warning signs may serve as a clinical indicator for heightened vigilance toward cardiac involvement. A multicentric study reported that patients with severe dengue and warning signs had a higher prevalence of conduction disturbances and repolarization abnormalities, corroborating our results [12].

Interestingly, not all warning signs correlated with ECG abnormalities. Persistent vomiting, lethargy/restlessness, and hepatomegaly did not show statistical significance in our cohort, which resonates with prior findings where systemic but non-hemodynamic warning signs lacked predictive value for cardiac dysfunction. This indicates that clinicians should prioritize cardiac monitoring when patients develop hemodynamic or respiratory warning signs rather than relying solely on gastrointestinal or constitutional symptoms [13].

From a pathophysiological standpoint, dengue myocarditis remains an under-recognized but increasingly reported complication. Case series from tertiary hospitals have demonstrated that early ECG changes, when correlated with warning signs, can serve as non-invasive markers for predicting myocardial involvement and impending complications [14]. Furthermore, advanced imaging and echocardiographic assessments, though not routinely feasible in resource-limited settings, have revealed subclinical cardiac dysfunction in patients with dengue, reinforcing the need for ECG as a cost-effective screening tool in endemic regions [15].

Thus, our findings support the incorporation of routine ECG evaluation in all hospitalized dengue patients, particularly those exhibiting warning signs. This approach can enable early identification of cardiac complications, guide timely intervention, and improve clinical outcomes.

Dengue infection can be associated with a wide range of cardiac manifestations, the most frequent being sinus bradycardia and other rhythm disturbances. In this study, ECG abnormalities showed significant correlations with several warning signs, including abdominal pain, mucosal bleeding, fluid accumulation, shock, respiratory distress, and ARDS, while others like persistent vomiting and hepatomegaly were not predictive of cardiac involvement. These findings highlight the importance of routine ECG monitoring in dengue patients, especially those with warning signs, to ensure early detection of cardiac complications and improved patient management

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