Pressure frequency characteristics of the pericardial space and thorax during subxiphoid access for epicardial ventricular tachycardia ablation

Background Nonsurgical subxiphoid pericardial access may be useful in ventricular tachycardia ablation and other electrophysiologic procedures but has a risk of right ventricular puncture. Objective The purpose of this study was to identify a signature pressure frequency that would help identify the pericardial space and guide access. Methods The study consisted of 20 patients (8 women and 12 men; mean age 59.1 ± 14.2 years; left ventricular ejection fraction 25.2% ± 12.2%; failed 1.8 ± 0.5 endocardial ablations; unresponsive to 2.0 ± 1.0 antiarrhythmic drugs; 6 ischemic cardiomyopathy, 12 nonischemic cardiomyopathy, 2 normal heart; 4 previous sternotomy) undergoing epicardial ventricular tachycardia ablation. After pericardial access was obtained, a 10Fr long sheath was used to record pressure inside the pericardium and pleural space. Pressures were analyzed using a fast Fourier transform to identify dominant frequencies in each chamber. Results Mean pressures in the pleural space and the pericardium were not different (7.7 ± 1.9 mmHg vs 7.8 ± 0.9 mmHg, respectively). However, the pericardial space in each patient demonstrated two frequency peaks that correlated with heart rate (1.16 ± 0.21 Hz) and respiratory rate (0.20 ± 0.01 Hz), whereas the pleural space in each patient had a single peak correlating with respiratory rate (0.20 ± 0.01 Hz). Conclusion The pericardial space demonstrates a signature pressure frequency that is significantly different from the surrounding space. This difference may make minimally invasive subxiphoid pericardial access safer for nonsurgeons and may have important implications for electrophysiologic procedures.