Cine magnetic resonance imaging detects shorter cardiac rest periods in postcapillary pulmonary hypertension

Abstract

Aims: A shorter cardiac rest period within a cardiac cycle is usually thought to be a result of a fast heart rate, and its clinical relevance has long been ignored. The aim of the present study was to test the hypothesis that the length of cardiac rest periods is altered in postcapillary pulmonary hypertension (PH).

Methods and results: Twenty-six patients with postcapillary PH and 20 healthy controls were recruited for cardiac magnetic resonance imaging (MRI) scans. All participants had a heart rate no higher than 80 beats/minute. Cine magnetic resonance imaging (MRI, acquired at a four-chamber view) was analyzed to determine the length of cardiac rest periods at end-systole and mid-to-late diastole. PH patients had a shorter rest period at mid-to-late diastole than controls (17.5 ± 8.7% vs. 24.2 ± 4.2%, P = 0.003). Receiver operating characteristic (ROC) curves showed that the proportion of the rest period in diastole (defined as the length of diastasis/diastole) can discriminate PH patients from controls [area under the curve (AUC) = 0.83, 95% confidence interval (CI): 0.71-0.96]. The existence of postcapillary PH was a significant contributor (β = -5.537, P = 0.023) to shorter cardiac rest periods at mid-to-late diastole after adjusting for potential confounders, including age, sex, heart rate, and blood pressure.

Conclusions: Postcapillary PH is independently associated with shorter cardiac rest periods at mid-to-late diastole. The length of cardiac rest periods has the potential to become a novel quantitative imaging biomarker for indicating cardiovascular health.

Keywords: cardiac rest periods; cine magnetic resonance imaging; postcapillary pulmonary hypertension.

Graphical Abstract

Figure 1

Four anchor points (represented using colour dots) at the septal and lateral sides of the LV and RV were traced on a four-chamber cine to track cardiac motion. The ‘rest period’ was defined as the motion of all four points ≤ 1 mm on adjacent frames. (A) End-diastole; (B) end-systole; (C) mid-to-late diastole; (D) relative positions of anchor points in cardiac cycles.

Figure 2

Cine MRI showed that the distributions of motion/rest periods within a cardiac cycle were different between controls and PH patients. Represented by the PWC, PH patients had shorter systole and diastasis (the rest period at mid-to-late diastole) but a longer rapid filling. There were no differences in the length of rest periods at end-systole or atrial contraction between the two subject groups.

Figure 3

ROC curves showed that the length of the rest period at mid-to-late diastole (represented by the PD, AUC = 0.83, 95% CI: 0.71–0.96) was better than age (AUC = 0.77, 95% CI: 0.62–0.91), BMI (AUC = 0.71, 95% CI: 0.56–0.86), sex (AUC = 0.63, 95% CI: 0.47–0.8), heart rate (AUC = 0.62, 95% CI: 0.46–0.78), SBP (AUC = 0.55, 95% CI: 0.37–0.72), and DBP (AUC = 0.67, 95% CI: 0.5–0.84) in discriminating postcapillary PH patients from controls.