Development Of Left Ventricular Outflow Tract Obstruction Research Articles

The Usefulness of Computed Tomography in Predicting Left Ventricular Outflow Tract Obstruction After Neonatal Arch Repair

This study investigated the outcome after neonatal arch repair, and the usefulness of computed tomography (CT) in predicting the development of left ventricular outflow tract (LVOT) obstruction (LVOTO). A total of 150 neonates who underwent arch repair between 2008 and 2019 were included. The diameters of the aortic valve annulus (AVA) and LVOT in millimeters were measured with transthoracic echocardiography (TTE) or CT and indexed by subtracting body weight in kilograms. The outcomes of interest were the development of LVOTO (peak flow velocity > 3 m/s on TTE) and reintervention or reoperation for LVOTO. The median follow-up duration was 3.6 years. The rates of overall survival, freedom from reintervention for LVOTO, and freedom from the LVOTO development at 7 years were 93.7%, 88.2%, and 81.0%, respectively. In univariable Cox regression analysis, weight-indexed CT-measured LVOT diameter (concordance index [C-index] = 0.73, P = 0.002) and weight-indexed TTE-measured AVA diameter (C-index = 0.69, P = 0.001) were significant predictors of LVOTO. The maximal chi-square test identified the following cutoff values for predicting LVOTO: 1.4 for weight-indexed CT-measured LVOT diameter and 1.6 for weight-indexed TTE-measured AVA diameter. The high-risk group (both measures lower than the cutoff values) had a significantly lower rate of freedom from LVOTO development than the low-risk group (both measures higher than the cutoff values) (P < 0.001). The weight-indexed CT-measured LVOT diameter could be used to predict LVOTO development after neonatal arch repair, as an independent measure or complementary to traditional measures.

Echocardiographic Predictors of Left Ventricular Outflow Tract Obstruction following Repair of Atrioventricular Septal Defect.

Left ventricular outflow tract obstruction (LVOTO) is a common complication following surgical repair of atrioventricular septal defect (AVSD). We sought to determine predictors of LVOTO based on echocardiograms performed prior to initial repair of AVSD. Of the 415 children that had repair of AVSD from 2003 to 2012, 17 children were identified with LVOTO that required surgical intervention. Thirty-four patients with repaired AVSD and no LVOTO served as controls. Patient demographics, cardiac surgery type, and echocardiogram results at last follow-up were collected. Off-line analysis of the echocardiogram prior to AVSD repair was done to obtain: left ventricular outflow tract (LVOT) and interventricular septal diameter, chordae across LVOT, aortoseptal angle, left ventricular (LV) inflow/outflow length ratio, inferior displacement of the atrioventricular (AV) valve, atrioventricular valve index (AVVI) and presence of coarctation of the aorta. The LVOTO group had significantly smaller indexed LVOT diameters (P < .001), increased likelihood of chordae crossing the LVOT (P = .010), decreased LV inflow/outflow length ratio (P < .001), decreased AVVI (P = .014) and increased presence of coarctation of the aorta (P = .003) compared to control patients. A multiple logistic regression model including presence of chordae in the LVOT [OR 5.32, 95% CI: (1.24-22.78, P = .024] and an indexed LVOT diameter ≤2.5 cm/m2 [OR 5.41, 95% CI: (1.15-25.39) P = .032] demonstrated each to be independently associated with the development of LVOT obstruction (area under the receiving operating curve = 0.77). Chordae across the LVOT and an indexed LVOT diameter of ≤2.5 cm/m2 are associated with a higher risk of development of LVOTO following repair of AVSD. Identification of these risk factors on echocardiogram prior to initial AVSD repair can be useful in evaluating for future risk of LVOTO and the need for closer clinical follow-up.

Role of noninvasive imaging modalities to better understand the mechanism of left ventricular outflow tract obstruction and tailored lesion-specific treatment options.

Left ventricular outflow tract obstruction (LVOTO) has important prognostic implications in patients with hypertrophic cardiomyopathy (HCM). Echocardiography provides critical information to establish LVOTO as a unique feature of HCM by demonstrating heterogeneity of hypertrophy patterns and the systolic anterior motion of mitral leaflets, resulting in mitral-septal contact. Currently, 2 treatment strategies are available for reduction of muscle mass to relieve LVOTO: surgical myectomy and percutaneous alcohol septal ablation. Both focus on mechanical removal of the hypertrophied septum. However, this alone is not the best approach to abolishing LVOTO, because recurrence is common and requires additional septal reduction. Recent 3-dimensional in vivo measurements and other noninvasive cardiac imaging modalities have confirmed primary alterations of the mitral valvular apparatus, including leaflet elongation with increased surface area and abnormal displacement of papillary muscles. More importantly, these extra-myocardial changes appear to be independent factors associated with the development of LVOTO. Other important anatomical changes include anomalous papillary muscle insertion into the anterior mitral leaflet and midventricular obstruction because of apposition of the hypertrophied mid-septum and the papillary muscle. Thus, the myocardium is not the only tissue affected in patients with HCM. A tailored approach to correcting primary changes of the mitral valvular apparatus and hypertrophy pattern based on a comprehensive evaluation using noninvasive imaging modalities is necessary to improve long-term outcomes.

The Relationship between Plasma Natriuretic Peptide Levels and Left Ventricular Function in Hypertrophic Cardiomyopathy at Rest and Peak Stress

Background: It has been shown that resting plasma levels of atrial natriuretic peptide (ANP) relate to exercise capacity in patients with hypertrophic cardiomyopathy (HCM). However, the relationship between natriuretic peptides and carQac structure and physiology, particularly with stress has not been determined in such patients. Methods: The relationships between plasma ANP and B-type natriuretic peptide (BNP) and left ventricular (LV) cavity measurements and function were investigated in 21 patients with HCM (age 54k16 years, 11 male), using Doppler echocardiography at rest and peak dobutamine stress (conventional protocol). All patients had normal LV systolic function (FS>30%). Results: All patients developed left ventricular outflow tract (LVOT) obstruction and dyspncea at peak stress (LVOT gradient at rest 31*24 mmHg. peak stress 1082.32, p<O.OOOI). Stress resulted in an increase in plasma levels of ANP (rest vs peak, 20.9k21.1 vs 31.a33.5 pmoVL) and BNP (31.2244.0 vs 45.368.6 pmoVL, both ~ 4 . 0 5 ) . AT REST levels of ANP and BNP were strongly correlated (Rz0.88, p<O.OOOI); ANP levels also correlated with LV dimensions (end diastolic R4.61; end systolic R4.45) and resting LVOT gradient (R=0.44, all p<0.05); BNP levels showed a similar correlation with LV dimensions (end diastolic R=0.67; end systolic R a . 4 9 , p<0.05) but not with LVOT gradient. AT STRESS: The two peptides remained closely related (R=0.91, p<O.OOOI). However, the association with LV measurements was lost. No association was found between peptide level and LVOT gradient at peak stress. Conclusion: Our results confirm previous findings in patients with heart failure, where resting natriuretic peptide levels correlate with ventricular function. It appears that the development of LVOT obstruction in patients with HCM severs this relationship. Despite this, ANP and BNP levels remain closely related. Further assessment of possible links with other indices of LV function is needed.