Hemodynamic data have always been, and remain, an integral part of all cardiovascular observations. Significant advances in both surgical and nonsurgical techniques for heart disease have been established in the last decade, in large part due to innovations both within and outside the cardiac catheterization laboratory. Many difficult forms of heart disease can now be readily confirmed with the improvement in two-dimensional and Doppler echocardiographic techniques. However, given the nature of clinical testing, there will always be suboptimal noninvasive examinations or patients in whom such testing cannot be performed. Thus, the catheterization laboratory remains critical to accurate measurements and the establishment of diagnoses. The presence of coexisting hemodynamic abnormalities in patients with coronary artery disease, myocardial infarction, or peripheral vascular disease cannot be established without direct information.
VASCULAR ACCESS AND SPECIAL CATHETERIZATION TECHNIQUES FOR OBTAINING HEMODYNAMIC DATA
Routine catheter access is obtained from the femoral artery and vein in most situations. The radial artery (and when needed, brachial vein) approach has gained acceptance and demonstrated reduced bleeding complications relative to femoral artery access. Many laboratories now use radial access as the default approach for routine cardiac cath.
Nonetheless, there are a variety of special access techniques which may be required for optimal hemodynamic assessment (table 1) [1-3].
- Transseptal access to the left atrium or ventricle is most often employed when prosthetic valves are located either in the aortic or mitral positions. Direct left atrial pressure measurement via the transseptal approach is also highly desirable, if not critical, to accurate decision making in conditions such as mitral stenosis, in which the pulmonary capillary wedge pressure is unreliable as a surrogate for the left atrial pressure. Under fluoroscopic guidance the transseptal access is obtained using a Brockenbrough catheter that is passed through the atrial septum over a needle that is used to puncture the septum at the fossa ovalis. This technique is commonly used for accurate assessment of mitral valve disease and as access for mitral balloon valvuloplasty.
- Direct left ventricular puncture through the left ventricular apex via the fifth intercostal space using echo-guided needle positioning is rarely used, but needed in patients with both aortic and mitral prosthetic valves. This technique is rarely used and carries significant excess risk.
- Catheters placed into the pericardial space when pericardial effusion is present may be necessary when determination of pericardial pressure is required for the assessment of clinical tamponade or congestive heart failure symptoms or hypotension of unexplained etiology.
- In some situations, special catheters are necessary for accurate recording. As an example, in the assessment of aortic stenosis, high fidelity manometer-tipped pressure catheters (or pressure sensor guidewire) are available to record small differences between aortic and left ventricular pressure. This technique can identify aortic gradients with improved precision when compared to fluid filled transducer systems. Double lumen catheters are also available. Improved ease of use these specialized catheters may gain future widespread application.
ROUTINE HEMODYNAMIC MEASUREMENTS
Routine hemodynamic measurements are obtained from the aorta (Ao), left ventricle (LV), right ventricle (RV), right atrium (RA), pulmonary artery (PA), and the pulmonary artery wedge position (for pulmonary capillary wedge pressure or PCWP); the last is usually equivalent to the left atrial (LA) pressure (figure 1).