Evaluation of Arterial Stiffness in Cardiac Surgical Patients Using Applanation Tonometry

Context

Applanation tonometry enables the noninvasive analysis of arterial pressure wave morphology. Applanation tonometry provides the augmentation index (AIx, %), an index of arterial stiffness that partially reflects arterial-ventricular (A-V) coupling. In addition, applanation tonometry provides the dP/dt (rate of intraventricular pressure variation over time), which reflects myocardial contractility, and the sub-endocardial viability ratio (SEVR, %), which is an indicator of myocardial oxygen supply and demand. There are no data on how cardiac surgery can modify these tonometry-derived indexes.

Aim

The aim was to assess changes in AIx, dP/dt, and SEVR in patients undergoing cardiac surgery.

Subjects and Methods

This observational study was conducted at the University Hospital of Siena. We studied 32 patients before cardiac surgery in intensive care unit (ICU) on admission and at ICU discharge. We measured AIx, dP/dt, and SEVR using applanation tonometry (SphygmoCor). Changes in variables over time were evaluated by analysis of variance for repeated measurements.

Results

AIx decreased significantly from T1 [28.8%, interquartile range (IQR) 21.6–36.6%] to T2 (16.2% IQR 8.1–22.4%) and T3 (14.5% IQR 7.9–23.6%) (P = 0.01). dP/dt increased significantly from T1 (635 mmHg/ms, IQR 534–756 mmHg/ms) to T3 (751 mmHg/ms, IQR 651–1013 mmHg/ms; P = 0.03). The SEVR was lower at T2 than at T1, but returned toward T1 values by T3.

Conclusions

Cardiac surgery was associated with an improvement in arterial stiffness, A-V coupling, and myocardial contractility as assessed using applanation tonometry. The results suggest, however, a transient imbalance between myocardial oxygen supply and demand in the immediate postoperative period.