Title: Echocardiographic Left Ventricular Z-score Utility in Predicting Pulmonary-Systemic Flow Ratio in Children with Ventricular Septal Defect or Patent Ductus Arteriosus
Authors: Sumitomo NF, Kodo K, Maeda J, Miura M, Yamagishi H
Circulation Journal 2022;86: 128-135, doi 10.1253/circj.CH-21-0559
Take Home Points:
- Left ventricular end diastolic dimension Z scores (cut point +1.76) have a good correlation (88% specificity overall and 96% specificity in children > 2 yo) with catheterization measured Qp:Qs (cQp:Qs) of 1.5 or more from a VSD or PDA.
- Left ventricular end systolic dimension Z scores also had a good correlation (72% specificity overall and 84% specificity in children > 2 yo) with cQp:Qs > 1.5 from a VSD or PDA.
- There was a reasonable correlation between echo derived and catheterization measured Qp:Qs with a r = 0.724
- This cannot be applied to patients with genetic abnormalities, to those with moderate or greater TR or MR or concomitant ASDs > 5 mm or defects other than VSD or PDA as this was not studied in this population
Commentary from Dr. Thomas Zellers (Dallas, USA), section editor of ACHD Journal Watch:
This is a good study that evaluates the correlation between cardiac catheterization measured pulmonary to systemic flow ratios, cQp:Qs, with echo predicted eQp:Qs and then with Z-scores for echo measured LV end-diastolic and LV end systolic dimensions.
The study applies only to patients with VSDs or PDAs. There were a lot of exclusions including patients with more than mild tricuspid, mitral, aortic or pulmonary valve regurgitation, atrial septal defects > 5 mm, any patient with genetic abnormalities, low birth weight (< 2500 gms) or premature infants, patients with poor growth (SD <-2), age < 1 month, PAH with mean PA pressure of 40 mmHg or more, RV systolic pressure > 70% of systemic pressure, and LVEF < 55%.
The authors started with 175 patients evaluated between 2015 and 2019 at two centers in Tokyo and ended with 70 patients in the study because of all of the exclusions. All patients had a cardiac catheterization with Qp:Qs measurements using the Fick method and all had a transthoracic echo with imaging and Doppler within one week of the cardiac catheterization. The LVEDd and LVESd dimension were measured using a standardized M-mode format for each patient. One echocardiographer, blinded to cardiac catheterization data, reassessed all echo measurements and, to determine intra- and inter-observer variations, a sample of patient measurements were evaluated by 4 blinded physicians. The Z-scores were derived from Patterson’s methods. Patients were also divided into younger than and older than 2 years of age and comparisons made between the two age groups.
The authors found a strong and significant correlation between the cQp:Qs and LVEDd. Using regression analysis, the LVEDd Z-score of 1.76 served as a cut point for a cQp:Qs of 1.5:1 or greater with a specificity of 88% for the cohort and 96% in the children more than 2 years of age.
In addition, the authors found a statistically significant correlation with the LVESd and cQp:Qs with a Z-score of 1.1 as a cut point for a cQp:Qs of 1.5 or greater. The sensitivity was 89% with a specificity of 72%.
While the correlation between cQp:Qs and eQp:Qs was good with an r = 0.724, the eQp:Qs is overestimated compared to cQp:Qs between 1 and 1.5:1 and is underestimated as the cQp:Qs values exceeded 2:1.
Limitations: This was a retrospective study from two centers with a modest sized group of patients (n=70) due to exclusions in a limited data set (VSD or PDA). The measured dimensions were taken from M-mode only but the inter and intra observer variability was low.