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Real-Time Left Ventricular Pressure-Volume Loops During Percutaneous Mitral Valve Repair With the MitraClip System
Study Questions:
What are the acute hemodynamic effects of the MitraClip device in patients with significant mitral regurgitation (MR)?
Methods:
The study examined changes in pressure-volume loops and hemodynamics in 33 patients treated with the MitraClip device. All patients had at least moderate to severe MR and were considered at high risk for traditional surgery. Measurements were performed using a conductance catheter and a right heart catheter.
Results:
Mean age was 78 ± 10 years, and 42% were female. Median hemodynamic variables (pre- vs. post-) associated with placement of the MitraClip device included an increase in end-systolic volume (57 vs. 84 ml, p = 0.006), no change in end-diastolic volume (147 vs. 138 ml, p = 0.18), decreased end-diastolic pressure (14 vs. 11 mm Hg, p = 0.002), decreased pulmonary capillary wedge pressure (15 vs. 12 mm Hg, p < 0.001), and increased cardiac index (2.6 vs. 3.2 L/min/m2, p < 0.001). With device placement, end-systolic wall stress (afterload) increased (184 vs. 209 mm Hg, p = 0.001) and end-diastolic wall stress (preload) decreased (48 vs. 34 mm Hg, p = 0.005). There was no significant correlation between change in cardiac index and end-systolic wall stress (r = 0.004, p = 0.98), although a significant linear relationship was observed between change in end-diastolic wall stress and change in pulmonary capillary wedge pressure (r = 0.63, p < 0.001). The pressure-volume loop area, a measure of total mechanical energy, was unchanged with device placement (9169 vs. 8634 mm Hg * ml, p = 0.66); the ratio of cardiac output to total mechanical energy significantly increased (p = 0.007).
Conclusions:
The authors concluded that MR treatment with a MitraClip device acutely improves left ventricular hemodynamics despite an increased afterload.
Perspective:
While there have been concerns regarding the small reported drop in left ventricular ejection fraction in patients undergoing the MitraClip procedure and other mitral valve procedures, the present findings are reassuring. Despite an acute increase in afterload, this appears to be outweighed by an acute decrease in preload, with improved hemodynamics, including an increased cardiac index and a decreased pulmonary capillary wedge pressure. Further, an acute increase in index of cardiac output to total mechanical energy was observed, suggesting improved cardiac efficiency following mitral valve repair. Future larger studies may be useful to identify which patients have the most significant hemodynamic benefit from mitral valve procedures, and to determine whether these hemodynamic changes are associated with improved clinical outcomes.
Keywords: Pulmonary Wedge Pressure, Ventricular Pressure, Ventricular Function, Left, Mitral Valve Insufficiency, Cardiac Output, Stroke Volume, Blood Pressure, Cardiac Surgical Procedures, Angioplasty, Balloon, Coronary, Cardiac Catheters, Hemodynamics
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