Fetal growth of left-sided structures and postnatal surgical outcomes in the “borderline” left heart varies by cardiac phenotype.
Venardos A, Colquitt J, Morris SA. Ultrasound Obstet Gynecol. 2021 May 16. doi: 10.1002/uog.23689. PMID: 33998097
Take home points:
- The authors in this study demonstrates that the growth of left sided cardiac structures in utero varies by the phenotype observed on fetal echocardiogram. Those with severe left heart hypoplasia but with an apex-forming left ventricle and without aortic stenosis (“long and skinny”) grow at a faster rate than those with severe aortic stenosis.
- This work informs fetal cardiologists to counsel parents of fetuses with left heart hypoplasia and an apex-forming left ventricle that the left-sided structures are likely to grow and there is high likelihood of biventricular repair. In contrast, with severe fetal aortic stenosis there is minimal growth of left-sided structures over gestation.
Commentary from Dr. Manoj Gupta (New York City, NY, USA), chief section editor of Pediatric & Fetal Cardiology Journal Watch:
Two “borderline” left heart phenotypes are encountered in the fetus: the “short, fat” globular left ventricle (LV) with systolic dysfunction, and the “long, skinny” LV in which the LV is apex-forming and systolic function is typically preserved. The “short, fat” phenotype is classically seen with severe aortic stenosis (AS) that has progressed past a stage of LV dilation. In the “long, skinny” phenotype, the LV is apex forming and hypoplastic in short axis dimension, has laminar flow across hypoplastic mitral and aortic valves, and arch hypoplasia is present. This phenotype is often termed “left heart hypoplasia” (LHH), “hypoplastic left heart complex”, or “Shone complex variant”.
Inclusion criteria for the severe AS group were: aortic annulus Z score <-2.0, severe AS defined as either minimal antegrade flow across the aortic valve (regardless of flow velocity) or evidence of valve narrowing with peak velocity >3 meters/second, patent aortic valve on first study, qualitatively depressed LV systolic function (to any degree), retrograde systolic flow in the arch, and endocardial fibroelastosis present at any point in gestation.
Inclusion criteria for the LHH group were: aortic annulus Z-score <-2.0, apex forming but narrow LV, qualitatively normal LV function, absence of endocardial fibroelastosis, and retrograde systolic flow in the aortic arch in the absence of atrial septal aneurysm. Retrograde systolic flow in the arch is very important in this group as this is indicative of the more severe form of LHH.
For each echocardiogram, two dimensional measurements of the aortic valve annulus, mitral valve annulus, LV short axis dimension, LV long axis length, distal transverse arch, and aortic isthmus were collected.
At the first fetal echocardiogram, fetuses with LHH had a later gestational age, larger aortic annulus diameter, and larger LV long axis dimension. There was no significant difference in initial arch measurements or LVED short axis dimension. The mean rate of aortic annulus growth was faster in the LHH group compared to the AS group. In the AS cohort, 3 (15%) died prior to intervention, 15 (75%) underwent single ventricle palliation, and 2 (10%) underwent biventricular repair. In the LHH cohort, 1 (3.1%) died prior to intervention, 3 (9.4%) underwent single ventricle palliation, and 28 (87.5%) underwent biventricular repairs (n=22) or no surgeries (n=6)
*Arch advancement is a repair via sternotomy for long segment arch hypoplasia using entirely native tissue. **One LHH patient who had initial biventricular repair ultimately required single ventricle palliation
This study demonstrates that the aortic annulus and other left sided structures (mitral valve and left ventricle) grow at a faster rate in fetuses with severe LHH than in fetuses with severe AS. A majority of infants in the AS group underwent single ventricle palliation, while a majority of infants in the LHH group had a biventricular circulation.
Overall mortality was higher in AS (11/20, 55%) compared to LHH (3/32, 9%). While the mortality in the AS group is quite high, this includes patients whose families chose comfort care.
The aortic valve, mitral valve, and LV do continue to grow throughout gestation at a faster rate in the LHH group than in the AS group. Still, the majority of those with LHH underwent biventricular repair while most of those with AS underwent single ventricle repair. In current practice, fetuses with severe AS and those with severe LHH may both counseled that the left-sided structures may not grow well, and that a single ventricle palliation is likely postnatally. However, we have shown that counseling should be targeted to the fetal cardiac phenotype.