Longitudinal echocardiographic parameters before and after pacemaker placement in congenital complete heart block

BACKGROUND

Congenital complete heart block (CCHB) is seen in 1:15,000-1:20,000 live births, with risk of left ventricular (LV) dysfunction or dilated cardiomyopathy in 7%-23% of subjects.

OBJECTIVE

The purpose of this study was to investigate serial changes in LV size and systolic function in paced CCHB subjects to examine the effect of time from pacemaker on echocardiographic parameters.

METHODS

Single-center retrospective cohort analysis of paced CCHB subjects was performed. Echocardiographic data were collected before and after pacemaker placement. Linear mixed effect regression of left ventricular end-diastolic dimension (LVEDD) z-score, left ventricular shortening fraction (LVSF), and left ventricular ejection fraction (LVEF) was performed, with slopes compared before and after pacemaker placement.

RESULTS

Of 114 CCHB subjects, 52 had echocardiographic data before and after pacemaker placement. Median age at CCHB diagnosis was 0.6 [interquartile range 0.0-3.5] years; age at pacemaker placement 3.4 [0.5-9.0] years; and pacing duration 10.8 [5.2-13.7] years. Estimated LVEDD z-score was 1.4 at pacemaker placement and decreased -0.08 per year (95% confidence interval [CI] -0.12 to -0.04; P = .002) to 0.2 (95% CI -0.3 to +0.3) 15 years postplacement. Estimated LVSF decreased -1.1% per year (95% CI -1.7% to -0.6%; P <.001) from 6 months prepacemaker placement to 34% (95% CI 32%-37%) 4 years postplacement. There was no significant change in LVSF between 4 and 15 years postplacement. Estimated LVEF did not change significantly after pacemaker placement, with estimated LVEF 59% (95% CI 55%-62%) 15 years postplacement.

CONCLUSION

In 52 paced CCHB subjects, estimated LVEDD z-score decreased significantly after pacemaker placement, and estimated LVSF and LVEF remained within normal limits at 15 years postpacemaker placement.

Incidence of Morbidity and Mortality in a Cohort of Congenital Complete Heart Block Patients Followed Over 40 Years

BACKGROUND

Congenital Complete Heart Block (CCHB), seen in 1:15,000-20,000 births, commonly requires pacemaker placement by young adulthood. There is limited understanding of cardiac morbidity and mortality.

OBJECTIVE

Determine long-term incidence of cardiac morbidity and mortality in subjects with CCHB and identify associated risk factors.

METHODS

Retrospective cohort analysis of subjects with CCHB at Children's Hospital of Philadelphia between 1976-2018. The primary outcome is a composite of death, left ventricular systolic dysfunction, heart failure, cardiomyopathy, or cardiac resynchronization therapy (CRT). Cox proportional hazard models assessed independent risk factors for the primary outcome and its components (death, heart failure and/or cardiomyopathy, CRT).

RESULTS

One-hundred-fourteen subjects (58% female, median age at last visit 15.2 years) were included. Eighty-eight (77%) underwent pacemaker implantation, with median age at placement 1.9 years (IQR, 0.1-8.0 years). Twenty-six subjects (23%) reached the primary outcome - 7 (6%) died and 14 (12%) were diagnosed with heart failure and/or cardiomyopathy. Median time from diagnosis to primary outcome was 3.1 years (IQR, 0.0-10.8 years). There were no significant associations between age at diagnosis less than 1-year (hazard ratio [HR]: 1.5, 95% CI 0.6-3.9), fetal diagnosis (HR: 2.3, 0.96-5.6), or maternal antibody positivity (HR: 2.4, 0.9-6.6) and the primary outcome. Fetal diagnosis had a higher associated hazard of heart failure and/or cardiomyopathy (HR: 4.5, 1.3-15.0).

CONCLUSION

In 114 subjects with CCHB, 23% reached the composite outcome of cardiac morbidity and mortality, with no significant association between age at diagnosis, fetal diagnosis, and maternal antibody status with composite cardiac morbidity and mortality.

End-Organ Function and Exercise Performance in Patients With Fontan Circulation: What Characterizes the High Performers?

Background The physiologic hallmarks of the Fontan circulation-chronically elevated central venous pressures and low cardiac output-have significant effects not only on cardiovascular status but also impact other organ systems. Exercise capacity is limited in many and declines with age, accelerating in adolescence, but with wide variability. We explore the relationship between exercise performance and end-organ function in outpatient subjects with a Fontan circulation. Methods and Results This is a cross-sectional analysis of subject end-organ characterization from our outpatient Fontan circulation clinic with peak oxygen consumption (peak Vo₂) at cardiopulmonary exercise testing as the primary outcome. We perform linear regression to assess associations between clinical characteristics and peak Vo₂ as well as the magnitude of the association of clinical characteristics with peak Vo₂. Of 265 subjects age 12.8 (9.5-16.4) years, there is a negative correlation between age and peak Vo₂ (-0.49, P<0.001). Of those undergoing ramp cycle exercise testing, 34% perform above 80% predicted peak Vo₂. Variables positively associated with peak Vo₂ and their effect size include vitamin D sufficiency (+3.00, P=0.020) and absolute lymphocyte count (+0.23, P=0.005). Status as overweight/obese (-3.91, P=0.003) and hemoglobin (-0.77, P=0.003) are negatively associated. Neither ventricular morphology, timing of Fontan palliation, nor Fontan circulation type affect peak Vo₂. Conclusions Higher peak Vo₂ in those with a Fontan circulation is associated with younger age, vitamin D sufficiency, absence of overweight/obese, lower hemoglobin, and a healthier hepatic profile. Whether exercise training or other initiatives can modify organ characteristics in those with a Fontan circulation is worthy of exploration.