Abnormal Wave Reflections and Left Ventricular Hypertrophy Late After Coarctation of the Aorta Repair

Abstract

Patients with repaired coarctation of the aorta are thought to have increased afterload due to abnormalities in vessel structure and function. We have developed a novel cardiovascular magnetic resonance protocol that allows assessment of central hemodynamics, including central aortic systolic blood pressure, resistance, total arterial compliance, pulse wave velocity, and wave reflections. The main study aims were to (1) characterize group differences in central aortic systolic blood pressure and peripheral systolic blood pressure, (2) comprehensively evaluate afterload (including wave reflections) in the 2 groups, and (3) identify possible biomarkers among covariates associated with elevated left ventricular mass (LVM). Fifty adult patients with repaired coarctation and 25 age- and sex-matched controls were recruited. Ascending aorta area and flow waveforms were obtained using a high temporal-resolution spiral phase-contrast cardiovascular magnetic resonance flow sequence. These data were used to derive central hemodynamics and to perform wave intensity analysis noninvasively. Covariates associated with LVM were assessed using multivariable linear regression analysis. There were no significant group differences (P≥0.1) in brachial systolic, mean, or diastolic BP. However central aortic systolic blood pressure was significantly higher in patients compared with controls (113 versus 107 mm Hg, P=0.002). Patients had reduced total arterial compliance, increased pulse wave velocity, and larger backward compression waves compared with controls. LVM index was significantly higher in patients than controls (72 versus 59 g/m², P<0.0005). The magnitude of the backward compression waves was independently associated with variation in LVM (P=0.01). Using a novel, noninvasive hemodynamic assessment, we have shown abnormal conduit vessel function after coarctation of the aorta repair, including abnormal wave reflections that are associated with elevated LVM.

Keywords: blood pressure; congenital heart disease; hemodynamics; hypertension; magnetic resonance imaging.

Figure 1.

Wave intensity analysis in representative repaired coarctation patient (A–D) and Control (E–H). Three main types of waveforms were found to arise during systole in study participants using wave separation analysis: (1) A forward compression wave, characterized by: increasing area and increasing flow representing cardiac ejection, B and F, labeled “*” (2) A protodiastolic forward expansion wave: decreasing area (pressure) and decreasing flow, B and F labeled “‡,” and (3) A backwards compression wave: increasing area (pressure) and decreasing flow, B labeled “†” (not seen in F in this particular control). The identification of the waves as compression or expansion can be seen from examination of C and G, showing the dA±plots. Time=0 corresponds to the onset of data acquisition as triggered by the R wave on cardiovascular magnetic resonance vectorcardiograph. D and H, Conventional wave separation analysis with the area waveform separated into forward and backward area waveforms. Vertical dotted lines added to assist visualization of wave timing.

Figure 2.

Positive (dI+) and negative wave intensity (dI−) in 1-dimensional simulation of (1) normal aorta (blue), (2) repaired coarctation, coarctation index [CI], 0.75 with normal isthmus stiffness (green), and (3) repaired coarctation, CI, 0.75 with stiff aortic isthmus (red). Units of wave intensity are conventional W/m². Note scale of dI− increased relative to dI+ to assist visualization.