Thanh Nguyen, MS4
The Article: Mediratta, Anuj, et al. "Echocardiographic diagnosis of acute pulmonary embolism in patients with McConnell's sign." Echocardiography 33.5 (2016): 696-702.
The Idea: The incidence of acute pulmonary embolism (aPE), which carries high rate of morbidity and mortality, has been rising in both the US and Europe. “McConnell’s sign” is an echocardiographic description that will increases suspicion of diagnosis of aPE. However, the diagnostic power of McConnell’s sign varies greatly between different studies. Myocardial strain, which is a new imaging technology, can quantitatively measure the heart muscle mechanical function. This study compares the use of different right ventricular (RV) functional parameters, in addition to McConnell’s sign, to differentiate patients with and without aPE
The Study: This study was a retrospective study performed in University of Chicago Medical Center in 2016
Inclusion Criteria: Patients who had undergone clinically indicated transthoracic echocardiograms (TTE) for suspected aPE and were determined to have a McConnell’s sign. Confirmed diagnosis of PE was made with either positive CT or a high probability for PE on V/Q scans.
Exclusion Criteria: Patients’ echocardiogram that were lack of adequate RV focused free wall views of quality suitable for strain analysis.
There was a total of 81 patients with positive McConnell’s sign who were divided into PE and non-PE group based on their confirmatory tests results. The study also included a group of 40 normal control who had no known heart disease or cardiac abnormality on echocardiography. Their TTE images were reviewed by an independent echocardiographer for presence of McConnell’s sign. Apical four chamber RV-focused view were imported into strain analysis software. Multiple RV functional parameters were measured, which included RV free wall segmental longitudinal strain, RV fractional area change (FAC), tricuspid annular plane systolic excursion (TAPSE), early tricuspid annular velocity (TDIS’), pulmonary artery systolic pressure (PASP) and severity of tricuspid regurgitation. Parameters and combination of parameters which were found significantly different were subjected to ROC analysis for their diagnostic power.
Primary Endpoint:
1) Compare RV functional parameters between patients who had McConnell’s sign and patients who were in normal control group.
2) Compare RV functional parameters between patients who were in PE and non-PE group
Secondary Endpoint:
1) Identify a single or combination of RV indices that had the strongest diagnostic power to differentiate PE and non-PE
The Result: The were a total of 55 of 81 (68%) patients with McConnell’s sign on TTE, who had PE diagnosis while 26 of 81 (32%) did not have PE. Compared to normal control, in patient with McConnell’s sign, conventional parameters of RV function and RV free wall strain were significantly lower. In McConnell’s sign +PE group, compared to non-PE group, the FAC, PASP, tricuspid regurgitation were significantly lower. The RV free wall strain was also significantly lower in PE group. In the non-PE group, 18 of 26 patient (69%) were found to have underlying primary or secondary pulmonary hypertension. Among parameters that were significantly different between PE and non-PE group, the TR severity, PASP, free wall strain and FAC had the highest diagnostic power in that descending order. Optimal cutoff of these parameters resulted in sensitivities in the range of 0.75 to 0.84, specificity 0.50 to 0.58, and accuracy 0.69 to 0.75. Combination of parameters that required either one or two or three resulted in high sensitivities >0.90 but low specificities. On the other hand, combination of parameters that required two or three criteria to be met simultaneously, the specificities improved to 0.75 to 0.88 while sensitivity reduced to 0.53 to 0.71.
The Takeaway: Although, McConnell sign has been used for decades as one of the diagnostic parameters of PE, its diagnosis accuracy is not high. However, McConnell sign may be a better indicator of RV function because patient with McConnell sign had significant lower value across measured RV functional parameters. Specifically, patient with McConnell’s sign, after being ruled out of PE, should undergo evaluation for pulmonary hypertension. The limitation of the study is its retrospective nature and relatively small number of studied patients. In addition, by combining 2-3 more RV functional parameters criteria with the presence of McConnell sign, specificity and accuracy for diagnosing PE are both higher while sensitivity remains the same.