The cardiac effects imposed by the novel H1N1 influenza strain have not been elucidated until now. Electrocardiographic (ECG) abnormalities were evaluated in a series of 50 patients with confirmed novel H1N1 influenza infection. Epidemiologic and clinical characteristics, laboratory correlations, and the effect ECG abnormalities may exert on disease outcomes were prospectively studied. Of the 50 patients, 14 (28%) exhibited ECG changes on admission. Nine patients presented with T-wave inversions, while ST-segment depression was observed on the electrocardiograms of 6 patients. The presence of ECG changes did not correlate with age, gender, co-morbidities, the laboratory profiles of the patients, or the coexistence of lower respiratory tract involvement. None of the patients exhibited alterations in cardiac-specific biochemistry or cardiac ultrasonography. All ECG changes were transient and reversed during disease regression. Two patients with ECG changes and 1 with normal ECG findings required intensive care, the former 2 eventually dying. Among the remainder, the duration of hospitalization did not exhibit a significant difference between the 2 groups, although there was a trend toward fewer days of hospitalization in the patients with ECG changes. In conclusion, ECG abnormalities are frequently encountered during novel H1N1 influenza infection, but their presence does not indicate a direct pathogen effect to the myocardium; these alterations may necessitate admission in the first place but are transient and not correlated with preexisting patient characteristics or with outcomes.
The evolution of the novel swine-origin influenza A (2009 H1N1 influenza) pandemic has imposed numerous therapeutic challenges, partly due to the different population groups targeted by the pathogen, resulting in different sets of experts dealing with the infection, but also due to differences in clinical presentation of the acute infection. It is thus of significant importance to elucidate clinical manifestations of a novel pathogen causing a pandemic, because sheer patient volume allows certain rare clinical manifestations to be recorded. We herein present the electrocardiographic (ECG) abnormalities encountered in a series of patients admitted to the hospital with novel H1N1 influenza and outline the presence or absence of risk factors of such abnormalities, as well as the prognostic significance they exert on patient outcomes.
Methods
All patients admitted to the Internal Medicine Department of the General Hospital “G. Hatzikosta” of Ioannina, Greece, with the diagnosis of novel H1N1 infection were included in this study. Diagnosis was confirmed by real-time polymerase chain reaction on nasopharyngeal or oropharyngeal swabs. Electrocardiography was performed in all patients on presentation to the emergency department and subsequently daily. Typical laboratory screening was performed in all patients admitted. All patients with ECG abnormalities were further evaluated with ultrasonography for underlying or ongoing heart disorders and by serial assessments of serum cardiac troponin I and creatine kinase-MB values. Risk factors for the presence of ECG abnormalities evaluated included age, gender, co-morbidities, isolated laboratory parameters such as lymphocyte number and hepatic biochemistry disturbances, and the involvement of the lower respiratory tract as shown by chest imaging. Outcome parameters evaluated included death, admission to the intensive care unit (ICU), and the duration of hospitalization.
Because this was an observational study with no interventions beyond typical medical care administered, no ethics committee approval was warranted.
Results
Fifty patients were admitted to the Internal Medicine Department with definite diagnoses of novel H1N1 influenza infection. Of these, 14 patients exhibited ECG abnormalities on admission. The epidemiologic, clinical, and laboratory characteristics of the 14 patients with ECG abnormalities and the 36 patients with persistently normal ECG findings are listed in Table 1 . The ECG abnormalities encountered are listed in Table 2 .
| Variable | ECG Alterations | Statistical Significance (p Value) | |
|---|---|---|---|
| Yes | No | ||
| (n = 14) | (n = 36) | ||
| Median age (years) | 34 | 36 | 0.76 |
| Male patients | 6 (43%) | 20 (56%) | 0.43 |
| Preexisting co-morbidities | 6 (43%) | 16 (44%) | 0.92 |
| Preexisting bronchial asthma | 3 (21%) | 5 (14%) | 0.52 |
| Lymphocyte percentage in whole blood count | 23% | 23% | 0.91 |
| Increase in liver aminotransferases | 3 (21%) | 5 (14%) | 0.52 |
| Positive imaging findings for lower respiratory tract involvement | 11 (78%) | 23 (64%) | 0.32 |
| Need for intensive care | 2 (14%) | 1 (3%) | 0.12 |
| Death | 2 | 0 | 0.018 ⁎ |
| Duration of hospitalization (in patients not necessitating intensive care) (days) | 2.8 | 3.8 | 0.12 |
| Age | Gender | ECG Alterations | Comments |
|---|---|---|---|
| 15 | Female | ST-segment depression (V 2 , V 3 ) | |
| 15 | Female | ST-segment depression (II, III, aVF, V 2 , V 3 ) | |
| 16 | Male | ST-segment depression (II, III, aVF) | |
| 16 | Female | T-wave inversion (II, III, aVF, V 1 , V 2 ) | Transient upper-normal-limit serum troponin I increase |
| 22 | Male | ST-segment depression (V 2 to V 4 ) | |
| 22 | Male | T-wave inversion (II, III, aVF) | |
| 24 | Male | ST-segment depression (V 4 to V 6 ), T-wave inversion (II, III, aVF) | |
| 28 | Female | T-wave inversion (III) | |
| 31 | Male | ST-segment depression (II, III, aVF, V 1 , V 2 ) | |
| 41 | Female | T-wave inversion (III) | Death |
| 54 | Female | T-wave inversion (V 2 to V 6 ) | |
| 57 | Male | T-wave inversion (III) | |
| 64 | Female | T-wave inversion (II, III, aVF) | Death |
| 72 | Female | T-wave inversion (II, III, aVF, V 3 to V 6 ) |
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