ECG Changes During Infection
Infections can cause multiple ECG abnormalities including ST-segment changes, T-wave inversions, arrhythmias, conduction disturbances, and QT prolongation—with these changes often being transient and reversible as the infection resolves.
Cardiac-Specific Infections
When infections directly involve cardiac structures, ECG changes are expected and clinically significant:
- Myocarditis produces ECG changes that warrant serial monitoring to assess disease progression and response to therapy 1
- Pericarditis typically shows diffuse ST-segment elevation (or more frequently PR depression) across multiple leads, representing inflammation rather than ischemia 2
- Endocarditis can cause ECG abnormalities that require serial ECGs for monitoring therapeutic response 1
Systemic Infections Without Direct Cardiac Involvement
Even infections without direct myocardial involvement frequently produce ECG changes:
COVID-19 Infection
- Up to 90% of critically ill COVID-19 patients demonstrate at least one ECG abnormality 3
- Common findings include sinus tachycardia (most frequent), ST-segment depression, T-wave inversions, ST-T changes, fragmented QRS, atrial fibrillation, and QT prolongation 4, 3
- ST depression (28% vs 14%), T-wave inversion (29% vs 16%), and fragmented QRS (17% vs 7%) occur more frequently in severe versus non-severe COVID-19 4
- ECG abnormalities associated with worse outcomes include atrial fibrillation, QT prolongation, ST-T changes, QRS duration ≥110ms, left bundle branch block, and ventricular arrhythmias 5, 3
- These changes can occur in young athletes without clinical or imaging evidence of myocarditis 6
Influenza (H1N1)
- 28% of H1N1 patients exhibit ECG changes on admission, most commonly T-wave inversions and ST-segment depression 7
- All ECG changes are transient and reverse during disease regression without evidence of direct myocardial pathogen effect 7
- Changes do not correlate with cardiac biomarkers or echocardiographic abnormalities 7
Mechanisms of Infection-Related ECG Changes
The pathophysiology involves multiple mechanisms beyond direct myocardial invasion 3:
- Cytokine storm and systemic inflammatory response
- Hypoxic injury from respiratory compromise
- Electrolyte abnormalities (particularly potassium and calcium disturbances)
- Coronary microthrombosis and endothelial dysfunction
- Coronary plaque rupture or spasm in susceptible patients
- Direct endothelial or myocardial injury in some cases
Clinical Implications and Monitoring
Serial ECGs are warranted during active infection until the disease process stabilizes 1:
- Obtain baseline ECG on admission for any patient with known or suspected cardiac involvement from infection 1
- Repeat ECGs to monitor disease progression and therapeutic response 1
- The frequency of serial ECGs depends on clinical severity and may require recordings over minutes, hours, days, or weeks 1
Important Caveats
- Not all ST-segment changes represent ischemia—pericarditis, electrolyte disturbances, and inflammatory changes can mimic acute coronary syndrome 2
- The absence of elevated cardiac biomarkers or echocardiographic abnormalities does not exclude ECG changes during infection 7
- ECG changes during infection may necessitate admission but their presence alone does not consistently predict outcomes in all infection types 7
- Certain ECG findings (atrial fibrillation, prolonged QRS, left bundle branch block, ST-T changes) independently predict mortality in severe infections like COVID-19 5, 4