Cardiac Catheterization

TECHNICAL ASPECTS OF CARDIAC CATHETERIZATION

Assessment of hemodynamics and gradients in mitral valve disease often necessitates simultaneous measurement of intracardiac pressures. This is even more important in the presence of concomitant pathological conditions that affect left heart hemodynamics such as aortic valve disease, hypertrophic cardiomyopathy, and precapillary pulmonary hypertension. Choice of access is based on the roadmap for planned assessment in a particular patient. For venous access, internal jugular or brachial access is necessary if exercise hemodynamics are to be assessed. Transseptal access for direct measurement of left atrial pressure requires transfemoral venous access. Simultaneous aortic and left ventricular measurements could be performed with a dual lumen such as Langston Pigtail Catheter (Teleflex, Wayne, PA, USA) or simultaneous placement of pigtail catheters in aorta and left ventricle from two arterial access points. Smaller sized 4F and 5F diagnostic catheters reduce vascular complications, however larger diameter catheters should be used if hemodynamic tracings are of inadequate quality. Left ventricle pressures should be measured with catheters with side holes. Specifically, we recommend only using side-hole pigtail catheters for performing ventriculogram and left ventricular pressure measurements. All hemodynamic measurements should be performed prior to contrast administration. Fluid-filled catheters used to obtain hemodynamic tracings should not be of excessive length because the natural frequency falls below the physiologic range, causing an overamplification of signal, leading to falsely elevated hemodynamic readings. The opposite effect, damping, a loss of physiologic signal occurs most often due to air trapped in the circuit and rarely due to formation of small thrombi in smaller diameter systems. Mean pulmonary artery wedge pressure reflects mean left atrial pressure, however the severity may be overestimated due to delay in transmission of pressure contour through the pulmonary circulation resulting in a phase shift compared to left ventricular end-diastolic tracing. Other potential causes such as under wedging could be corrected my checking oxygen saturation in wedge position.

A transseptal puncture may be necessary on rare occasions when wedge tracings are inadequate or unreliable to guide therapeutic decisions. Intracardiac echocardiography (ICE) or transesophageal echocardiography (TEE) use enhances safety of transseptal approach. Use of ICE obviates the need for additional operators and general anesthesia during the procedure. The puncture should be performed using left anterior oblique (LAO) projections, and a Brockenbrough needle is passed through the fossa ovalis, until a jump across the septum into the left atrium is noticed and confirmed by change in the pressure waveform. The dilator and sheath are advanced over the needle. The dilator and needle are then withdrawn. We use an NRG RF transseptal needle (Baylis Medical, Montreal, Quebec, Canada) which uses radio frequency (RF) energy, delivered through a closed-tip device. The manufacturer recommends a single 10W pulse delivered over a period of 2 seconds. The main advantage is eliminating the need for mechanical pressure, and hence reducing excessive “jump” and possible complications of catheter exit. Other alternative approaches include the SafeSept transseptal device (Pressure Products, San Pedro, CA, USA), which uses J-shaped terminal nitinol wire with a sharpened end, and the TransLas catheter (LasCor GmbH, Taufkirchen, Germany), which uses laser energy.

When performing left ventriculogram for assessing mitral regurgitation, large bore side-hole catheters should be used and it is necessary to use large enough contrast amount to completely opacify the cardiac chambers, to avoid underestimation of lesion severity. Contrast injection should be timed to avoid ventricular ectopy. The injection should be fast enough to quickly opacify the chambers but slow enough to avoid stimulating the ventricle causing ectopy. To avoid contrast being superimposed on a background of spine or descending aorta, high right anterior oblique views are often required.