Interventricular Mechanical Asynchrony in Pulmonary Arterial HypertensionLeft-to-Right Delay in Peak Shortening Is Related to Right Ventricular Overload and Left Ventricular Underfilling
J. Tim Marcus, PhD*,*,
C. Tji-Joong Gan, MSc ,1,
Jaco J.M. Zwanenburg, PhD ,2,
Anco Boonstra, MD, PhD,
Cor P. Allaart, MD, PhD ,
Marco J.W. Götte, MD, PhD and
Anton Vonk-Noordegraaf, MD, PhD
* Department of Physics and Medical Technology, Institute for Cardiovascular Research, VU University Medical Center, Amsterdam, the Netherlands
Department of Pulmonary Diseases, Institute for Cardiovascular Research, VU University Medical Center, Amsterdam, the Netherlands
Department of Cardiology, Institute for Cardiovascular Research, VU University Medical Center, Amsterdam, the Netherlands
Image Sciences Institute, University Medical Center Utrecht, Utrecht, the Netherlands.
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Figure 1 MRI Cine and Tagged Images
Three-chamber images (top panels), short-axis images (middle panels), and short-axis tagged images (bottom panels), at the time of aortic valve closure at trigger delay of 252 ms (left) and the time of peak right ventricular (RV) shortening at 341 ms (right). The 3-chamber images show that maximal leftward septal bowing occurs at 341 ms, well after aortic valve closure. In the tagged image at 341 ms, the distance of the tagging lines in the RV free wall show further shortening (thick white arrows), whereas the tagging lines in the left ventricular (LV) free wall show relaxation. MRI = magnetic resonance imaging.
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Figure 2 Circumferential Strain Over Time, PAH Patient
Circumferential strain curves over time after the electrocardiographic R-wave for the left ventricular (LV) and right ventricular (RV) free walls and the septum for 1 patient at basal level. The LV, RV, and septum start simultaneously with shortening (negative strain), but the RV reaches its peak later than the LV, by 12% of the cardiac cycle time. The closure times of aortic and pulmonary valves (Taortacl and Tpulmcl) are coincident with the peak of LV shortening. The time of maximal leftward septal bowing (Tlvsb) is coincident with septal stretching (positive strain) and with the peak of RV shortening. The opening times of mitral and tricuspid valves (Tmitr-op and Ttric-op) indicate the onset times of LV and RV filling. PAH = pulmonary arterial hypertension.
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Figure 3 Circumferential Strain Over Time, Healthy Subject
Similar to Figure 2 but for a healthy control subject. The RV reaches its peak slightly earlier than the LV, but LV and RV start relaxation simultaneously, and the septum does not overstretch. Abbreviations as in Figure 2.
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Figure 4 Timing Parameters
Timing parameters presented by mean values and SDs (error bars), for the 21 pulmonary arterial hypertension patients. ECG = electrocardiogram; L = left ventricle; R = right ventricle; S = septum; Taortacl = closure time of aortic valve; Tivsb = time of maximal leftward septal bowing; Tonset = onset time of circumferential shortening; Tpeak = peak time of circumferential shortening; Tpulmcl = closure time of pulmonary valve.
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Figure 5 L-R Delay Versus RV Wall Tension
Linear regression between the left-to-right (L-R) delay in time to peak of circumferential shortening (Tpeak) normalized for the R to R interval (RR) as dependent variable and the right ventricular (RV) wall tension, p = 0.01, r = 0.54.
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Figure 6 From RV Overload to Loss of Stroke Volume
Flowchart of the proposed mechanism by which RV overload relates to a left-to-right delay in peak shortening, which relates to the loss of stroke volume in PAH. Only correlations were studied, so the cause-effect relationships in this flowchart are only a tentative postulated model. Abbreviations as in Figure 2.
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