Room Setup/Design/Equipment

The setup and design for the hybrid cardiac catheterization OR is covered separately in Chapter 26. This section reviews the importance of radiation safety and physician credentialing. For the individual laboratory, the monitoring suite is separated from the x-ray imaging equipment by lead-lined glass, as well as lead-lined walls. Voice communication from the central area is maintained with each catheterization laboratory to coordinate tasks performed in the central area (e.g., monitoring and recording data, activated coagulation time [ACT] determination), thereby minimizing staff radiation exposure.¹⁰ A picture of a representative catheterization laboratory is shown in Figure 3-1.

Figure 3-1 A representative cardiac catheterization laboratory.

The x-ray tube is located below the table, and the flat-panel detector is located above the table, both mounted on a “C” arm. Shielding, image monitors, and emergency equipment can also be seen.

Radiation Safety

Radiation safety must be considered at all times in the catheterization laboratory, from room design to everyday practice.¹¹ Lead-lined walls, lead-glass partitions, and mobile lead shielding are useful in limiting the daily exposure of personnel.

A thermoluminescent film badge must be worn at all times by any personnel exposed to the X-ray equipment, with levels monitored regularly. In the past, anesthesiologists responding to emergencies in the catheterization laboratory were exposed to radiation briefly and infrequently (if at all). With the requirement for anesthesiologists in many of the newer multidisciplinary procedures, the inclusion of anesthesiologists in formal monitoring programs may be appropriate. Radiation levels should not exceed 5 rem per calendar year, and 1.25 rem per calendar quarter, or approximately 100 mrem per week.¹² Operator and staff radiation have been assessed for years. However, only recently has the issue of radiation toxicity to the patient gained attention. With long PCI and electrophysiology procedures, radiation injury to the patient has been identified, and the need for monitoring dose delivery to the patient is now appreciated.¹³ Contemporary equipment estimates radiation doses to the patient, and recordings of theses doses are made. Lead aprons are mandatory for all personnel in the procedure suite. For those who need shielding for extended periods, lead apron and vest combinations may be more comfortable. Often cumbersome, these shields protect the gonads and about 80% of the active bone marrow.¹¹ Thyroid and eye shielding also should be considered, particularly for those working in close proximity to the x-ray source.¹⁴

It is not in the scope of this chapter to cover all aspects of radiation. For a more complete review of this topic, a consensus document was published by the American College of Cardiology/American Heart Association/Heart Rhythym Society/Society of Cardiovascular Angiography and Interventions.¹⁵

Several aspects of radiation safety require a brief review. The duration of the procedure will increase exposure. Cine imaging (i.e., making a permanent recording) requires about 10 times the radiation of fluoroscopy. Although newer equipment may narrow this ratio and permanently record fluoroscopic images, limiting cine imaging will decrease exposure. Proximity to the x-ray tube, usually situated below the patient, is directly related to exposure. The bulk of the radiation exposure to medical personnel is the result of scattered x-rays coming from the patient. When working in an environment where x-rays are in use, clinicians should always remember the simple rule of radiation dose: The amount of radiation exposure is related to the square of the distance from the source. No body part should ever be placed in the imaging field when fluoroscopy/cine is being performed. Finally, the cardiologist can decrease x-ray scatter by placing the imaging equipment as close to the patient as possible, thereby decreasing personnel exposure.¹⁶

The anesthesiologist should recognize x-ray use in the catheterization laboratory and take appropriate precautions. For multidisciplinary procedures, this requires some attention to the location of equipment and the use of portable shields. It also is worth noting that most lead aprons have openings in the back, and protect best when the wearer is facing the source of the x-rays. Emergent situations, when the anesthesiologist is asked to resuscitate a critically ill patient during a procedure, may require the cardiologist to use fluoroscopic imaging while the anesthesiologist is within feet of, and often even straddling, the x-ray tube. With 96% of the x-ray beam scatter stopped with 0.5 mm of lead, aprons and thyroid shields clearly are neccessary to protect the anesthesiologist while at the head of the patient.¹¹ The use of x-rays can almost always be interrupted to protect personnel; patient care may require the interruptions to be brief. A collaborative effort between the cardiologist and the anesthesiologist is necessary, and communication is essential. The goal of the anesthesiologist should be to treat the patient while protecting himself or herself from excess radiation.¹⁵

Filmless Imaging/Flat-Panel Technology

Essentially all modern laboratories use filmless or digital recording. Radiation is required to generate an image and recordings are made at various frequencies (frames/sec). The best image quality for film is produced at x-ray frame rates of more than 30 frames/sec. Digital imaging decreases radiation exposure in the laboratory by allowing for image acquisition at lower frame rates, 15 frames/sec (half the radiation dose), while still maintaining excellent image quality. Cost savings have been achieved by the elimination of the purchasing, processing, and storage of film. Film imaging was an analog technique, and a single recording was made. Copies rarely were made because of cost and degradation of image quality. If films were loaned, lost, or misplaced, the study could not be reviewed. With the current digital technology, images are archived on a central server and can be viewed on remote workstations.¹⁷ An infinite number of copies can be made at low cost and with no loss of image quality.

Data compression for storage is required to be 2:1 (“lossless”) compression. Although “lossless” compression on a CD-ROM is the standard for the transfer of images between institutions, similar standards do not exist for long-term archival (no media standard) and data transfer options within a single institution (no compression standard).¹⁸ Large amounts of memory and bandwidth are required for storage and transfer of the images in “lossless” compression. At remote viewing stations, such as those in the OR, it is essential that the viewer be aware of the type of image compression used to transfer data. If significant image compression is used, image quality will decrease. It is essential that improper decisions not be made because of inferior image quality.

The evolution of angiographic recording has extended beyond recording formats. Charged-couple device cameras and flat-panel detectors (FPDs) are ubiquitous in modern laboratories.¹⁹ x-rays are generated from below the patient by the x-ray tube, pass through the patient, and are captured by the FPD. In this system, the x-rays are both acquired and digitally processed by the flat panel.¹⁵ The flat panel is above the patient (analogous to the image intensifier), and the x-rays are generated below the patient, as before. This current generation of imaging in the catheterization laboratory delivers an improved image quality because the dynamic range of the image (number of shades of gray) is improved. It has the potential to decrease radiation exposure by providing immediate feedback to the x-ray generator. In laboratories designed for peripheral vascular work, including many of the hybrid ones, the sizes of the FPD above the patient can be quite large and may limit access to the patient’s face.

Facility Caseload

All catheterization facilities must maintain appropriate patient volume to assure competence. ACC/AHA guidelines recommend that a minimum of 300 adult diagnostic cases and 75 pediatric cases per facility per year be performed to provide adequate care.¹² A caseload of at least 200 PCIs per year, with an ideal volume of 400 cases annually, is recommended.^20–22

Facilities performing PCIs without in-house surgical backup are becoming more prevalent.^23,24 Despite this, national guidelines still recommend that both elective and emergent PCIs be performed in centers with surgical capabilities.^22,25 Although emergent coronary artery bypass graft surgery (CABG) is infrequent in the stent era, when emergent CABG is required, the delays inherent in the transfer of patients to another hospital would compromise the outcomes of these compromised patients.²² Primary PCI for acute myocardial infarction (AMI) is the accepted standard treatment for the following patients: (1) those in cardiogenic shock, (2) those who have contraindications to thrombolytic therapy, and (3) those who do not respond to thrombolytic therapy. It is preferred therapy for those who present late in the course of an infarction, and is probably the optimal treatment for all myocardial infarctions (MIs), provided that it can be performed in a timely manner.^26–28 When a patient presents with an AMI to a facility without cardiac surgical capabilities, management is controversial. Although national guidelines do not endorse the performance of PCI in this setting, they state that the operator should be qualified. In practice, this means that he or she performs elective and emergent PCIs at another facility and the total laboratory case volume should be at least 36 AMI procedures per year.²⁶

Although minimal volumes are recommended, no regulatory control currently exists. In a study of volume-outcome relationships published for New York State, a clear inverse relation between laboratory case volume and procedural mortality and CABG rates was identified.²⁹ In a nationwide study of Medicare patients, low-volume centers had a 4.2% 30-day mortality rate, whereas the high-volume centers’ mortality rate was 2.7%.³⁰ The ACC clinical competence statement for PCI summarizes these studies.²¹ Centers of excellence, based on physician and facility volume, as well as overall services provided, may well be the model for cardiovascular care in the future.³¹

Physician Credentialing

The more experience an operator has with a particular procedure, the more likely this procedure will have a good outcome. The American College of Cardiology (ACC) Task Force has established guidelines for the volume of individual operators in addition to the facility volumes mentioned earlier.¹² The current recommendations for competence in diagnostic cardiac catheterization require a fellow to perform a minimum of 300 angiographic procedures, with at least 200 catheterizations as the primary operator, during his or her training.

Prior guidelines have recommended a cardiologist perform a minimum of 150 diagnostic cases per year to maintain clinical expertise after fellowship training.^12,32 Of note, when physicians have performed more than 1000 cases independently, the individual case volume may decline for a limited period with the operator still maintaining a high level of expertise. The ideal case volume should not exceed 500 to 600 procedures per year for physicians committed to cardiac catheterization. For the physician performing pediatric procedures, annual volumes should equal or exceed 50 cases.¹² Ultimately, each hospital’s quality assurance/peer review program is responsible for setting its own standards and maintaining them through performance improvement reviews.^33,34

In 1999, the American Board of Internal Medicine established board certification for interventional cardiology. To be eligible, a physician has to complete 3 years of a cardiology fellowship, complete a (minimum) of a 1-year fellowship in interventional cardiology, and obtain board certification in general cardiology. In addition to the diagnostic catheterization experience discussed earlier, a trainee must perform at least 250 coronary interventional procedures. Board certification requires renewal every 10 years, and initially was offered to practicing interventionalists with or without formal training in intervention. In 2004, the “grandfather” pathway ended, and a formal interventional fellowship is required for board certification in interventional cardiology. After board certification, the physician should perform at least 75 PCIs as a primary operator annually. Operators who perform fewer than 75 cases per year should operate only in facilities that perform more than 600 PCIs annually. In addition to caseload, the physician should attend at least 30 hours every 2 years in interventional cardiology continuing education.²² With the establishment of board certification for PCI and the correlation of outcomes to PCI volumes, it is likely that high-volume, board-certified interventional cardiologists will displace low-volume PCI operators, and improved outcomes will result.^23,24

The performance of peripheral interventions in the cardiac catheterization laboratory is increasing. Vascular surgeons, interventional radiologists, and interventional cardiologists all compete in this area. The claim of each subspecialty to this group of patients has merits and limitations. Renal artery interventions are the most common peripheral intervention performed by interventional cardiologists, but distal peripheral vascular interventions are performed in many laboratories. Stenting of the carotid arteries looks favorable when compared with carotid endarterectomy.³⁵ Guidelines are being developed with input from all subspecialties. These guidelines and oversight by individual hospitals will be necessary to ensure that the promise of clinical trials is translated into quality patient care.

With this in mind, internal peer review is essential for the catheterization laboratory. Although separate from credentialing, the peer review process is designed to identify quality issues for the purpose of improving patient care. This involves education, clinical practice standardization, feedback and benchmarking, professional interactions, incentives, decision-support systems, and administrative interventions.^12,34 An internal peer review process allows the physicians to establish and maintain in-hospital practice standards essential for quality patient care.

Indications for Cardiac Catheterization in the Adult Patient

Table 3-1 lists generally agreed-on indications for cardiac catheterization. With respect to CAD, approximately 15% of the adult population studied will have normal coronary arteries.¹² This reflects limitations of the specificity of the clinical criteria and noninvasive tests used to select patients for catheterization. However, as the sensitivity and specificity of the noninvasive studies have improved, this percentage of normal studies has progressively declined.³⁶ Despite this, coronary angiography is, for the moment, still considered the gold standard for defining CAD. With advances in MRI and multislice CT scanning, the next decade may well see a further evolution of the catheterization laboratory to an interventional suite with fewer diagnostic responsibilities.¹

TABLE 3-1 Indications for Diagnostic Catheterization in the Adult Patient

Patient Evaluation before Cardiac Catheterization

Diagnostic cardiac catheterization in the 21st century universally is considered an outpatient procedure except for the patient at high risk. Therefore, the precatheterization evaluation is essential for quality patient care. Evaluation before cardiac catheterization includes diagnostic tests that are necessary to identify the high-risk patient. An electrocardiogram (ECG) must be performed on all patients shortly before catheterization. Necessary laboratory studies before catheterization include a coagulation profile (prothrombin time [PT], partial thromboplastin time [PTT], and platelet count), hemoglobin, and hematocrit. Electrolytes are obtained together with a baseline blood urea nitrogen (BUN) and creatinine (Cr) to assess renal function. Recent guidelines express a preference for estimation of glomerular filtration rate (GFR) using accepted formulae. Many clinical laboratories now report this value routinely. Urinalysis and chest radiograph may provide useful information but are no longer routinely obtained by all operators. Prior catheterization reports should be available. If the patient had prior PCI or CABG surgery, this information also must be available.

The precatheterization history is important to delineate the specifics that may place the patient at increased risk. Proper identification of prior contrast exposure with or without contrast allergic reaction must be recorded. If a true contrast reaction (rash, breathing difficulties, angioedema, and so forth) occurred with prior contrast exposure, premedication with glucocorticoids is required. Diabetes, preexisting renal insufficiency, and heart failure are widely accepted risk factors for contrast-induced nephropathy (CIN). A Cr level greater than 1.5 mg/dL, particularly in a patient with diabetes, or a GFR less than 60 mL/min should prompt special precautions.³⁷ The study can be canceled or delayed. If the indication for catheterization is strong, prehydration, avoidance of certain medication (e.g., nonsteroidal anti-inflammatory drugs), and limiting the volume of contrast (i.e., assessing ventricular function by echocardiography and omitting ventriculography) will reduce the risk for worsening renal function.¹²

A review of the noninvasive cardiac evaluation before cardiac catheterization allows the cardiologist to formulate objectives for the procedure. In patients with hypotension on the exercise stress test, left main coronary lesions should be suspected. Knowing the location of either perfusion or wall-motion abnormalities in a particular coronary distribution, the cardiologist must specifically identify or exclude coronary lesions in these areas during the procedure. Finally, in patients with echocardiographic evidence of left ventricular (LV) thrombus, left ventriculography may not be performed.

Patient medications must be addressed. On the morning of the catheterization, antianginal and antihypertensive medications are routinely continued, whereas diuretic therapy is withheld. Diabetic patients are scheduled early, if possible. As breakfast is withheld, no short-acting insulin is given. Patients on oral anticoagulation should stop warfarin sodium (Coumadin) therapy 48 to 72 hours before catheterization (international normalized ratio ≤ 1.8) if femoral arterial access is used. Radial arterial access is considered an option without discontinuation of Coumadin.³⁸ This, however, may present its own challenges and laboratory protocols should be established to address this. In patients who are anticoagulated for mechanical prosthetic valves, the patient may be managed best with intravenous heparin before and after the procedure, when the warfarin effect is not therapeutic. Low-molecular-weight heparins (LMWHs) are used in this setting, but this is controversial. LMWHs vary in their duration of action, and their effect cannot be monitored by routine tests. This effect needs to be considered, particularly with regard to hemostasis at the vascular access site. Intravenous heparin is routinely discontinued 2 to 4 hours before catheterization, except in the patient with unstable angina (UA). Aspirin therapy for patients with angina or in patients with prior CABG is often continued, particularly in patients with UA.³⁹

Contraindications, High-Risk Patients, and Postcatheterization Care

Despite advances in facilities, equipment, technique, and personnel, the precatheterization evaluation must identify those patients at increased risk for complications. In a modern facility with an experienced staff, the only absolute contraindication would be the refusal by a competent patient or an incompetent patient unable to provide informed consent. Relative contraindications are listed in Box 3-1; the primary operator is responsible for this assessment.¹²

Box 3-2 lists criteria for identifying the high-risk patient before catheterization. Procedural alterations based on this assessment may include avoidance of crossing an aortic valve or performing ventriculography.⁴⁰ Regardless of the risk, determination as to whether a patient is a candidate for catheterization must be based on the risk versus benefit for each individual.

With the increased emphasis on outpatient procedures in medicine today, outpatient diagnostic catheterization is the standard of care for stable patients. Unstable and postinfarction patients are already hospitalized, and catheterization usually is performed before discharge. Planned PCI usually requires admission. Even when outpatient catheterization is planned, assessment of the patient after catheterization is required. Some patients, particularly those with left main CAD, critical aortic stenosis, uncontrolled hypertension, significant LV dysfunction with congestive heart failure, or significant postprocedural complications such as a large groin hematoma will require hospital admission.¹²

In addition to the high-risk cardiac patient, patients with renal insufficiency may require overnight hydration before and after catheterization. Patients on chronic anticoagulation with warfarin (Coumadin) require measurement of the coagulation status and may require heparinization before and/or after the procedure. Day-of-procedure ambulation and discharge are planned for patients undergoing outpatient catheterization.³⁷ Radial catheterization is increasing in popularity and is associated with a reduction of vascular complications.^38,41 For a variety of reasons, the sheaths used for radial access are not suitable for long-term monitoring purposes and should be removed at the conclusion of the procedure. For patients undergoing catheterization via the percutaneous femoral approach, the use of smaller catheters (4 French) for the arterial puncture may hasten ambulation.⁴² Alternatively, a variety of vascular closure devices are approved for use.⁴³ Vascular closure devices differ in the material that is used (and left in the patient). Some devices (i.e., Angio-Seal, St. Jude Medical) use an intraluminal anchor made of bioabsorbable material. However, it is recommended that the treated vessel not be used for repeat arterial access for up to 3 months, to permit absorption of the anchor and limit the risk for embolization. Protocols for early ambulation may permit the patient to be out of bed 2 to 4 hours after hemostasis, or even earlier if a closure device is used.⁴²

Patient Preparation

All patients receive a thorough explanation of the procedure, often including pamphlets and videotapes. A full explanation of technique and potential risks minimizes patient anxiety, and is similar to the preoperative anesthesia visit. It is important for the cardiologist to meet the patient before the study. This relaxes the patient while allowing the physician to be better acquainted with the patient, aiding in the decision process. Although some laboratories do allow the patient to have a clear liquid breakfast up to 2 to 3 hours before the procedure, outpatients are routinely asked to have no oral intake for 8 hours before the procedure, except for oral medications.

Patients with previous allergic reactions to iodinated contrast agents require adequate prophylaxis.⁴⁴ Greenberger et al.⁴⁵ studied 857 patients with a prior history of an allergic reaction to contrast media. In this study, 50 mg of prednisone was administered 13, 7, and 1 hour before the procedure. Diphenhydramine (50 mg intramuscularly) also was administered 1 hour before the procedure. Although no severe anaphylactic reactions occurred, the overall incidence of urticarial reactions in known high-risk patients was 10%. The use of nonionic contrast agents may further decrease reactions in patients with known contrast allergies.⁴⁴ The administration of H₂ blockers (300 mg cimetidine) is less well-studied.⁴⁴ For patients undergoing emergent cardiac catheterization with known contrast allergies, 200 mg of hydrocortisone is administered intravenously immediately and repeated every 4 hours until the procedure is completed. Diphenhydramine (50 mg intravenously) is recommended 1 hour before the procedure.⁴⁴

CIN is defined as an increase in serum Cr concentration of more than 0.5 mg/dL or 25% above baseline level within 48 hours.³⁷ Although infrequent, occurring in less than 5% of PCIs, when it does occur, its impact on patient morbidity and mortality is significant.⁴⁶ Total contrast doses less than 4 mL/kg are recommended in patients with normal renal function, and lower doses are recommended for those with preexisting renal dysfunction, particularly in diabetic patients (Cr > 1.5).³⁷ A study in more than 8000 PCI patients identified 8 risk factors for CIN: hypotension, intra-aortic balloon pump, congestive heart failure, chronic kidney disease, diabetes, age older than 75, anemia, and contrast volume.⁴⁷ It is, therefore, essential that the patient at high risk be identified and properly treated. In addition, renal function should be monitored for at least 48 hours in patients at high risk for CIN, particularly if surgery or other interventions are planned.

Several methods have been used to decrease renal toxicity from contrast agents. The two most important measures are minimizing contrast dose and adequate hydration with 0.9% saline at a rate of 1 mL/kg/hr for 12 hours before and after the procedure, if tolerated.³⁷ Low osmolar contrast agents are recommended.⁴⁸ Iso-osmolar contrast agents, treatment with N-acetylcysteine (Mucomyst) and sodium bicarbonate infusions, have yielded mixed results.^37,49,50 Fenoldopam, a dopamine agonist, has been studied and has shown no benefit.⁵¹ Ultrafiltration dialysis has been beneficial in small studies.³⁷

Patient Monitoring/Sedation

Standard limb leads with one chest lead are used for ECG monitoring during cardiac catheterization. One inferior and one anterior ECG lead are monitored during diagnostic catheterization. During an interventional procedure, two ECG leads are monitored in the same coronary artery distribution as the vessel undergoing PCI. Radiolucent ECG leads permit monitoring without interfering with angiographic data.

Cardiac catheterization laboratories routinely monitor arterial oxygen saturation by pulse oximetry (Spo₂) in all patients. Utilizing pulse oximetry, Dodson et al.⁵² demonstrated that 38% of 26 patients undergoing catheterization had episodes of hypoxemia (Spo₂