Methods

The medical records of hospitalized patients with a discharge diagnosis of acute PE were reviewed from January 2009 through December 2012. The institutional review boards of the participating hospitals (St. Mary Mercy Hospital, Livonia, Michigan; St. Joseph Mercy, Ann Arbor, Michigan; and McLaren Hospital, Pontiac, Michigan) approved the present investigation.

The included patients were aged ≥18 years, who had had PE diagnosed by multidetector computed tomographic (CT) pulmonary angiography and an electrocardiogram obtained the same day.

Patients with previous cardiopulmonary disease were excluded. Additional exclusions included patients with a history or present illness of coronary heart disease, cardiomyopathy, myocarditis, valvular heart disease, congenital heart disease, previous PE, lung or lobe resection, chronic obstructive pulmonary disease, emphysema, carcinoma of the lung, chronic bronchial asthma, and any chronic pulmonary disease.

The electrocardiograms were read by 1 of us (P.D.S.) according to previously described criteria. The readings were made without knowledge of whether the patients had RV cavity enlargement.

The ratio of the RV minor axis to the left ventricular (LV) minor axis was measured on the transverse images of the diagnostic CT pulmonary angiograms, using described previously methods. The RV/LV dimension ratios, calculated from the axial views of the CT pulmonary angiograms of the patients with PE, were equivalent to the RV/LV dimension ratios calculated from manually or computer-generated reconstructed 4-chamber views. We did not perform multiplanar reformatted reconstructions. An RV/LV dimension ratio >1 was defined as RV cavity enlargement.

Standard methods were used to calculate the sensitivity, specificity, and positive and negative predictive values. The probability of the difference in the prevalence was assessed by chi-square using GraphPad software (San Diego, California). Differences were considered statistically significant at p <0.05. Ninety-five percent confidence intervals were calculated using GraphPad software.

Results

Of the 1,516 patients with acute PE, 1,161 were excluded because of previous cardiopulmonary disease. Another 66 patients were excluded: 5 because the diagnosis was made by lung scans, 36 because no electrocardiogram had been obtained, and 25 who had undergone electrocardiography on days other than the day of the CT pulmonary angiogram. Thus, 289 patients were included, all of whom had undergone electrocardiography the same day as PE was diagnosed using CT pulmonary angiography. The patients with RV cavity enlargement were older than those with a normal RV size ( Table 1 ). The gender, racial distribution, proportion requiring ventilatory support, and in-hospital all-cause case fatality rate did not differ significantly between those with and without RV enlargement ( Table 1 ).

Normal ECG findings were less prevalent in patients with RV cavity enlargement than those with a normal RV size (35 of 141 [25%] vs 56 of 148 [38%]; p = 0.02). Normal ECG findings, other than the presence of sinus tachycardia, were also less prevalent in patients with RV enlargement (41 of 141 [29%] vs 69 of 148 [47%]; p = 0.002).

Sinus tachycardia, nonspecific T-wave changes, and ST-segment or T-wave changes, were more prevalent in patients with RV enlargement. The incidence of other ECG abnormalities did not differ significantly between those with and without RV enlargement ( Table 2 ). One or more of the traditional ECG manifestations of acute cor pulmonale (S1Q3T3, complete right bundle branch block, P pulmonale, or right axis deviation) was found in 18 of 141 patients (13%) with RV cavity enlargement and 13 of 148 (8.8%) with a normal RV size (p = NS).

None of the ECG abnormalities was sensitive for RV cavity enlargement ( Table 3 ). The specificity of P and QRS abnormalities was typically high for RV enlargement ( Table 3 ). The positive predictive values for RV enlargement were ≤83% for most ECG abnormalities ( Table 3 ). Three had positive predictive values of 100%, but their 95% confidence intervals were wide. The negative predictive values for RV enlargement ranged from 50% to 61% ( Table 3 ).

Table 3

Sensitivity, specificity, and positive and negative predictive values

Electrocardiographic Finding	Sensitivity (%)	95% CI	Specificity (%)	95% CI	PPV (%)	95% CI	NPV (%)	95% CI
Rhythm disturbances
Sinus tachycardia	29	22–37	82	76–88	61	49–72	55	48–61
Sinus bradycardia	2.1	0.7–6.1	95	91–98	30	11–60	51	45–56
Atrial fibrillation	1.4	0.4–5.0	100	97–100	100	34–100	52	46–57
Atrial flutter	2.1	0.7–6.1	97	93–99	43	16–75	51	45–57
Premature atrial contractions	5.7	2.9–11	97	92–99	62	36–82	52	46–58
Premature ventricular contractions	2.8	1.1–7.1	96	91–98	40	17–69	51	46–57
Atrioventricular conduction abnormalities
First-degree atrioventricular block	3.5	1.5–8.0	97	93–99	56	27–81	51	46–57
Second-degree atrioventricular block	0.7	0.1–3.9	100	97–100	100	21–100	51	46–57
P wave
Right atrial enlargement	1.4	0.4–5.0	99	96–100	67	21–94	51	46–57
Left atrial enlargement	0.7	0.1–3.9	99	96–100	50	9.5–91	51	45–57
QRS abnormalities
Right axis deviation	4.3	2.0–9.0	97	92–99	55	28–79	51	46–57
Left axis deviation	10	6.0–16	90	84–94	48	31–33	51	45–57
S1S2S3	11	7.1–18	92	86–95	57	39–73	52	46–58
S1Q3T3	7.1	3.9–13	97	92–99	67	42–85	52	46–58
Incomplete right bundle branch block	3.5	1.5–8.0	99	95–100	71	36–92	52	46–58
Complete right bundle branch block	4.3	2.0–9.0	97	93–99	60	31–83	52	46–57
RV hypertrophy	2.1	0.7–6.1	99	95–100	60	23–88	51	46–57
Incomplete left bundle branch block	0.0	0.0–2.7	99	96–100	0.0	0–79	51	45–57
Left bundle branch block	0.0	0.0–2.7	97	92–99	0.0	0–43	50	45–56
LV hypertrophy	0.0	0.0–2.7	96	91–98	0.0	0–29	50	44–56
Pseudo-infarction	0.7	0.1–3.9	98	94–99	25	4.6–70	51	45–57
Low voltage (frontal plane)	3.5	1.5–8.0	99	96–100	83	44–97	52	46–58
Clockwise rotation	14	9.4–21	92	88–95	63	45–77	53	47–59
Primary ST-segment and/or T-wave abnormalities
ST-segment depression	18	13–26	89	82–93	60	46–73	53	47–59
ST-segment elevation	2.1	0.7–6.1	99	96–100	75	30–95	52	46–57
Nonspecific T-wave changes	33	26–45	84	77–89	66	52–74	57	50–63
ST-segment and T-wave changes	2.1	0.7–6.1	100	97–100	100	44–100	52	46–57
ST-segment or T-wave changes	52	44–60	72	64–78	63	54–72	61	54–69

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