The Case:
A 58-year-old M with no reported PMHx presenting with shortness of breath and the following ECG. The patient endorses 1 week of exertional dyspnea that evolved to include pleuritic chest pain one hour prior to arrival. He had severe shortness of breath on awaking. He denied hemoptysis, lower extremity edema, calf pain, history of VTE, hormone use, recent surgery, or prolonged immobility.
Rate?
Rhythm?
Axis?
Intervals?
QRST?
Interpretation:
The ECG was notable for Sinus tachycardia, Normal axis, Normal intervals, and SI QIII TIII pattern.
Case Conclusion:
A point-of-care ultrasound was notable for a diminished TAPSE at 1.6 cm and McConnell sign. A CTA pulmonary embolism (PE) protocolled study was expedited, and gross read was notable for a right main pulmonary artery embolism. The PERT Team was activated, and the patient was transferred to the cath for aspiration thrombectomy within 1 hour of evaluation.
Discussion:
Pulmonary embolism is a frequently considered diagnosis in patients presenting with chest pain. Although findings of pulmonary embolism on ECG are frequently taught, ECG is overall neither sensitive nor specific for the diagnosis, with one study evaluating the ECGs of 189 consecutive patients diagnosed with both large clot load (n=76) and small clot load (n=113) PEs observed 20% to 25% had normal ECGs (1). Sinus tachycardia is described the most common abnormality observed with a prevalence of 44%. Although SI QIII TIII pattern was observed in this case, it is only present in approximately 20% of cases and, therefore, poorly sensitive and specific (2,3). Other findings associated with PE and their prevalence are complete or incomplete RBBB (18%), right ventricular strain pattern consisting of T wave inversions in V1-V4 with or without II,II, AVF (34%), right axis deviation (16%), right atrial enlargement consisting of a P wave in lead II > 2.5 mm (9%), atrial tachyarrhythmias (8%), and non-specific ST changes (50%) which is not considered the most common the discrete pattern is unpredictable.
Given the poor prevalence and nonspecific nature of ECG abnormalities in PE, the diagnostic utility of ECG is independently poor. Conversely, in those diagnosed with PE, ECG changes may have a prognostic value (3). A study comprised of 1,001 consecutively recruited patients with either submassive or massive PEs aim to evaluate this prognostic value. They found that atrial arrhythmias (88%), complete RBBB (87%), limb lead low voltage (79%), Q waves in leads III and aVF but not in II (93%), and ST elevation I, II, and V4-V6 (94%) were specific for 30-day mortality. Therefore, ECGs with these findings in those with concern for a submassive or massive PE should suggest rapid evaluation and specialist consultation.
Take away points:
1 in 4 patients, including those with large clot burdens, will have normal ECGs
Sinus tachycardia is the most common finding in PE
SI QIII TIII pattern independently has limited diagnostic utility
Atrial arrhythmias, complete RBB, low voltage in limb leads, Q waves in leads III and aVF but in II, and ST elevation in lateral and inferior leads are associated with higher mortality in those with submassive or massive PEs
Authored by Jose Reyes, MD
References:
Dakkak W, Doukky R. Sick Sinus Syndrome. [Updated 2023 Jul 17]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK470599/
Hafeez Y, Grossman SA. Junctional Rhythm. [Updated 2023 Feb 5]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK507715/
Semelka M, Gera J, Usman S. Sick sinus syndrome: a review. Am Fam Physician. 2013 May 15;87(10):691-6. PMID: 23939447.