Catheterization of the right and left sides of the heart can be accomplished by the introduction of catheters (a) by direct vision into the brachial vein and artery (9) or (b) by percutaneous puncture of the radial artery or femoral or brachial vein and artery (10). The choice of approach (brachial, femoral, or radial) for venous and arterial catheterization is determined by the preference and experience of the operator as well as by the anatomic and pathophysiologic abnormalities of the patient. In general, right-sided heart catheterization is easier via the brachial approach in the patient with right ventricular or right atrial dilatation. In contrast, in the patient with a secundum atrial septal defect, a right-sided heart catheter can be passed across the defect more easily via the femoral approach. Thus, in choosing the route for right-sided heart catheterization, it is necessary to be cognizant of anatomic abnormalities and specific disease entities. In most patients, left-sided heart catheterization can be performed by the radial, brachial, or femoral approach. However, the femoral approach offers several advantages. This approach can be performed quickly and repeatedly in the same patient, allows the use of larger-lumen catheters, and has a low incidence of infection or vascular injury. Certain conditions, however, render left-sided heart catheterization by the femoral approach difficult, such as extensive peripheral vascular disease, marked obesity, severe systemic arterial hypertension, bleeding diatheses, and any disorder that results in a markedly augmented arterial pulse pressure (e.g., severe aortic regurgitation). In the patient with any of these conditions, the brachial or radial approach may be safer if performed by an operator experienced with this technique. In turn, the brachial or radial approach for left-sided heart catheterization is relatively contraindicated if there is evidence of severe brachiocephalic or ulnar arterial disease.

In rare circumstances, placement of a catheter in the left ventricle across the aortic (or mitral) valve is not advisable. For
example, advancement of a catheter across a tilting disk prosthetic valve may result in catheter entrapment. Accordingly, direct puncture of the left ventricle through the chest wall can be performed to measure left ventricular pressure and to perform left ventriculography. With this approach, after generous local anesthesia, an 18-gauge needle is inserted at the apical impulse and is directed toward the long axis of the left ventricle (toward the right shoulder). When heart pulsations or ventricular ectopy are noted, the needle is in contact with the ventricular epicardium, and it is slowly advanced until pulsatile blood flow is observed. Left ventricular pressure can be measured directly through the needle. If ventriculography is to be performed, the needle can be exchanged over a guidewire for a 4- or 5-Fr pigtail catheter. Significant complications (cardiac tamponade, hemothorax, pneumothorax, ventricular fibrillation) occur in 3% to 10% of these procedures, and vasovagal reactions occur in approximately 5% (12).

Percutaneous endomyocardial biopsy may be performed to obtain pieces of myocardial tissue for microscopic examination. Most commonly, tissue is obtained from the right ventricle; however, left ventricular biopsy also can be performed. From the femoral or internal jugular vein, a long biopsy sheath with a side arm port is advanced to the right ventricle over a guidewire. Then, under fluoroscopic guidance, the bioptome is advanced through the long sheath and is directed toward the interventricular septum. After the bioptome has exited the end of the sheath, its jaws are opened, and it is advanced to the septum. The jaws are then tightly closed, and the bioptome is briskly withdrawn through the sheath to tear away a small piece of tissue. This procedure is repeated until three to five tissue specimens are obtained. Local complications related to vascular access (i.e., venous thrombosis, hemorrhage, pneumothorax, recurrent laryngeal nerve injury) are the most common problems associated with this procedure and occur in 1% to 2% of patients. Transient arrhythmias and right bundle branch block from catheter manipulation are common, but sustained rhythm abnormalities are not. Cardiac perforation is rare (13), occurring in less than 0.05% of procedures, but it may lead to pericardial tamponade and hemodynamic collapse, especially if it is not recognized promptly and treated appropriately. Other rare complications include tricuspid regurgitation (resulting from chordal tear) and formation of a fistula from the coronary artery to the right ventricle (14).

During routine right-sided heart catheterization, measurements of pressures and O₂ saturations in the venae cavae, right atrium, right ventricle, pulmonary artery, and pulmonary capillary wedge position can be performed, and CO can be quantified (Table 77.4 gives normal values). The measurement of right-sided pressures helps one to evaluate the severity of tricuspid or pulmonic stenosis, to assess the presence and severity of pulmonary hypertension, and to calculate pulmonary vascular resistance. In the absence of pulmonary vein stenosis (a rare condition), the pulmonary capillary wedge pressure accurately reflects left atrial pressure. The determination of O₂ saturations from the various right-sided heart chambers is used to assess the presence, location, and magnitude of intracardiac left-to-right shunting, such as occurs with atrial or ventricular septal defect or patent ductus arteriosus. Occasionally, angiography is performed to define right-sided anatomic abnormalities or to evaluate the severity of right-sided valvular regurgitation.

For optimal measurement of right-sided heart pressures, a relatively stiff, large-lumen, nonflotation catheter is used, which can be advanced until it “wedges” in a small pulmonary artery. The catheter’s position in the pulmonary capillary wedge location is confirmed by obtaining blood with an O₂ saturation greater than 95%. Alternatively, a softer, balloon-tipped flotation catheter can be used. With this catheter, the acquisition of a blood sample to confirm the pulmonary capillary wedge position is often difficult, and the fidelity of the pressure recordings obtained with it is less ideal than that obtained with a stiffer, large-lumen catheter; however, its ease of passage and paucity of complications make it more suitable for use by operators with limited experience. Furthermore, because it is flow directed, it often can be advanced through the right side of the heart without fluoroscopic guidance. Finally, addition of a thermistor to the flotation catheter’s distal portion allows one to measure CO by the thermodilution technique.

With left-sided heart catheterization, one can assess (a) mitral and aortic valvular function, (b) left ventricular pressures and function, (c) systemic vascular resistance, and (d) coronary arterial anatomy. To perform angiography or to measure the pressure in the left ventricle, one usually advances a catheter
in retrograde fashion across the aortic valve. In rare circumstances in which this is impossible (e.g., severe aortic stenosis or a tilting disk prosthetic valve in the aortic position), transseptal catheterization is performed, and the catheter is advanced to the left ventricle in antegrade fashion across the mitral valve.

During most catheterizations, pressures are measured directly from each of the cardiac chambers except the left atrium. The left atrial pressure is generally recorded “indirectly,” that is, as the pulmonary capillary wedge pressure. To accomplish this, an end-hole catheter is placed in the pulmonary artery and is advanced into the pulmonary arterial tree until it is effectively wedged. If the catheter is wedged adequately, the resultant pressure is left atrial, and the blood withdrawn from it is fully saturated. The demonstration that fully saturated blood can be withdrawn from the catheter confirms that the pressure is indeed left atrial. When a direct left atrial pressure recording is needed, a transseptal catheterization can be performed.

The flow of blood throughout the body is known as CO and is expressed in liters per minute. Because the magnitude of CO is proportional to body surface area, one person may be compared with another by means of the cardiac index (i.e., the CO adjusted for body surface area). The normal cardiac index is 2.6 to 4.2 L per minute per m² of body surface area (Table 77.4). The two commonly used methods of measuring CO are the Fick method and the indicator dilution technique.