Cardiac Catheterization - Diagnostic Evaluation of Cardiovascular Function

CARDIAC CATHETERIZATION

Cardiac catheterization is an invasive diagnostic procedure inwhich radiopaque arterial and venous catheters are introduced into selected blood vessels of the right and left sides of the heart. Catheter advancement is guided by fluoroscopy. Most commonly, the catheters are inserted percutaneously through the blood ves-sels, or via a cutdown procedure if the patient has poor vascular access. Pressures and oxygen saturations in the four heart cham-bers are measured. Cardiac catheterization is used to diagnose CAD, assess coronary artery patency, and determine the extent of atherosclerosis based on the percentage of coronary artery ob-struction. These results determine whether revascularization pro-cedures including PTCA or coronary artery bypass surgery may be of benefit to the patient.

During cardiac catheterization, the patient has an intra-venous line in place for the administration of sedatives, fluids, heparin, and other medications. Noninvasive hemodynamic monitoring that includes BP and multiple ECG tracings is nec-essary to continuously observe for dysrhythmias or hemody-namic instability. The myocardium can become ischemic and trigger dysrhythmias as catheters are positioned in the coronary arteries or during injection of contrast agents. Resuscitation equip-ment must be readily available during the procedure. Staff must be prepared to provide advanced cardiac life support measures as necessary.

Radiopaque contrast agents are used to visualize the coronary arteries; some contrast agents contain iodine. The patient is assessed before the procedure for previous reactions to contrast agents or allergies to iodine-containing substances (eg, seafood). If the patient has a suspected or known allergy to the substance, antihistamines or methylprednisolone (Solu-Medrol) may be administered before the procedure. In addition, the following blood tests are performed to identify abnormalities that may complicate recovery: BUN and creatinine levels, INR or PT, aPTT, hematocrit and hemoglobin values, platelet count, and electrolyte levels.

Diagnostic cardiac catheterizations are commonly performed on an outpatient basis and require 2 to 6 hours of bed rest before ambulation. For most patients, bed rest for 6 hours compared to 2 hours has no advantage with regard to groin bleeding compli-cations (Logemann et al., 1999). However, variations in time to ambulation are most often related to the size of the catheter used during the procedure, the anticoagulation status of the patient, other patient variables (eg, advanced age, obesity, bleeding dis-order), the method used for hemostasis of the arterial puncture site after the procedure, and institutional policies. The use of smaller (4 or 6 Fr) catheters, which are more amenable to shorter recovery times, is common in diagnostic cardiac catheterizations. There are several methods available to achieve arterial hemostasis after catheter removal, including manual pressure, mechanical compression devices such as the FemoStop (placed over puncture site for 30 minutes), and percutaneously deployed devices. The latter devices are positioned at the femoral arterial puncture site after completion of the procedure. They deploy collagen (VasoSeal), sutures (Perclose, Techstar), or a combination of both (Angio-Seal). Major benefits of these devices include reliable, immediate hemostasis and shorter time on bed rest without a significant increase in bleeding or other complications (Baim et al., 2000). A number of factors determine which hemostatic methods are used and are based on the physician’s preference, the patient’s condition, cost, and institutional availability of the equipment.

Patients hospitalized for angina or acute MI may also require cardiac catheterization. After the procedure, these patients usu-ally return to their hospital rooms for recovery. In some cardiac catheterization laboratories, an angioplasty may be performed immediately after the catheterization if indicated.