American College of Cardiology

A. The Cardiac Catheterization Laboratory Environment

Cardiac catheterizations are currently performed safely in hospitals with and without cardiac surgical backup. The latest information from the Society for Cardiac Angiography and Interventions lists >2100 cardiac catheterization laboratories in the United States (including Puerto Rico and the Virgin Islands) ⁽¹⁾. Of these, 72% provided on-site cardiac surgery (including 85% of those performing coronary intervention). Fifty-eight laboratories were located in nonhospital settings.

In a hospital with cardiac surgery, essentially all patients with cardiovascular disease can undergo invasive studies safely. Full support services include not only cardiovascular surgery but also vascular surgery, nephrology and dialysis, neurology, hematology, and specialized imaging services (e.g., computed tomography, magnetic resonance imaging, and ultrasound). See Table 7 for assessment of proficiency criteria for individual operators and cardiac catheterization laboratories.

In the hospital setting without cardiac surgery capability, many patients can undergo cardiac procedures safely. Exclusions for cardiac catheterization in this setting include patients with acute coronary syndromes, severe congestive heart failure, pulmonary edema due to acute ischemia, a high likelihood of severe multivessel or left main disease based on noninvasive testing, and severe left ventricular dysfunction associated with valvular disease. Certain elective therapeutic interventional procedures such as percutaneous coronary interventions (PCIs) and valvuloplasty should still be performed in facilities that provide cardiac surgical support. The ACC Competence Statement on Recommendations for the Assessment and Maintenance of Proficiency in Coronary Interventional Procedures and the ACC/AHA Guidelines for Percutaneous Coronary Interventional (PCI) Procedures ^(2,3) have addressed the issue of primary angioplasty for acute myocardial infarction in hospitals without cardiac surgery capability. Recent data suggest a lower mortality rate among patients undergoing primary angioplasty in higher-volume centers ⁽⁴⁾. Hospitals that perform primary angioplasty but are without on-site cardiac surgery capability must have a proven plan for rapid access (within 1 hour) to a cardiac surgical operating room in a nearby facility with appropriate hemodynamic support capability for such a transfer. The procedure should be limited to patients with ST-segment elevation MI or new LBBB on ECG, and done in a timely fashion (balloon inflation within 90±30 min of admission) by persons skilled in the procedure (75 PCIs performed per year) and only in facilities performing a minimum of 36 PCIs per year. In accordance with the soon-to-be-published ACC/AHA guidelines for PCI ⁽³⁾, this committee does not endorse the performance of elective PCI in a facility without cardiac surgery capability.

Patients are also being studied in freestanding laboratories (i.e. those that are not physically attached to the hospital). By definition a freestanding laboratory is one where quick transportation of a patient to a hospital by gurney is not possible. These patients clearly must be in stable condition and at the lowest risk for complications. It is vitally important to have mechanisms for backup and bailout in place to provide assistance should patients become unstable in this setting. Although a tertiary hospital serves as an appropriate means for providing proper oversight of a freestanding laboratory, recognized credentialing bodies approved by the local community may be able to provide appropriate oversight to ensure that all issues related to quality assurance are monitored and addressed. Interventional procedures of any kind should not be performed in a freestanding facility.

B. Same-Day and Outpatient Cardiac Catheterization

With the decline in risk associated with cardiac catheterization, the performance of invasive procedures in the ambulatory setting has become more popular. However, prehospitalization may still be important in patients receiving anticoagulation therapy or in those with renal failure, diabetes, or a contrast allergy. Early discharge after the procedure may also be inappropriate for certain patients, including those with a procedure-related complication or hemodynamic instability. In addition, some patients are best observed overnight if severe disease is discovered (e.g., significant left main coronary artery disease or severe aortic stenosis) or in the presence of significant comorbid diseases that increase the risk of late complications. A general scheme is presented to help determine who should be excluded from early discharge after cardiac catheterization.

C. Quality Assurance Issues

Quality assurance (QA) starts with an assessment of clinical proficiency among the operators in the cardiac catheterization laboratory. This is surely one of the most difficult elements to assess, but issues of cognitive knowledge, procedural skill, clinical judgment, and procedural outcomes are all important. QA extends to the performance of the laboratory as a whole. A continuous quality-improvement (QI) program should also be included in the laboratory's overall design.

One measure of outcome is the number of “normal” diagnostic cardiac catheterizations performed. “Normal” in this regard refers to no disease or insignificant (less than 50% diameter narrowing) coronary stenoses in patients studied primarily for the identification of coronary artery lesions. It is recognized that there is a difference between coronary arteries that are completely normal and those that have insignificant luminal stenoses. It is further recognized that coronary disease is a dynamic process and that endothelial dysfunction may contribute to certain clinical syndromes. In some laboratories “normal” coronary arteries may be especially prevalent because the patient mix includes a variety of disease states where coronary disease is not the major concern, such as cardiomyopathy and valvular disease. The rate of “normals” identified as either insignificant or no obvious luminal narrowing should be in the range of 20% to 27% if proper screening and baseline decision making is operative prior to the catheterization.

Outcomes related to complications for diagnostic catheterization should be very low—<1%. Diagnostic accuracy and adequacy are obviously important parameters as well, though they are rarely tracked. In the interventional cardiac catheterization laboratory the acceptable complication rates are more difficult to gauge, since measures of assessing high-risk patients have not been standardized. Major complications, (i.e. death, acute myocardial infarction, and emergency bypass surgery) from interventional procedures should be <3%.

The minimum number of studies needed to confirm adequate skills in cardiac diagnostic catheterization procedures has never been validated. Given the low risk of diagnostic catheterization, the QI system should be operative and should hold precedence over any arbitrary figures proposed in this setting. The Committee could find no data to support the prior recommendation for a minimum caseload of 150 catheterizations performed by an individual per year. A minimum interventional caseload is 75 cases per year per operator and ideally 400 cases per year for the laboratory. Because of the direct correlation between both laboratory and physician volume and outcomes, a low-volume operator (<75 cases per year) should only work in a high-volume laboratory (>600 cases per year), and even then with mentoring. Low-volume operators in any other setting should not perform interventional procedures. The minimum caseload for operators performing pediatric catheterizations has not been established by data, although a caseload of 50 per year has been suggested for individual operators. Pediatric cardiac catheterization laboratories often share space with adult procedural facilities. The pediatric catheterization laboratory should perform at least 75 procedures per year.

Equipment maintenance and management remain an issue, and certain guidelines are provided. Each aspect of the radiographic system should be able to meet these performance expectations. The same is true for the physiological recorders and other specific devices used in the laboratories.

A QI program must be in place. The keys are to develop variables that reflect the quality of care, to collect these variables in a systematic manner, to have a means for statistical analysis of the results, and to develop an approach to problem solving that involves feedback on the effectiveness of the solutions. These programs should provide ongoing educational opportunities for staff as well. The Committee also strongly encourages all laboratories to participate in a national data registry to help benchmark their results and provide an ongoing system for tracking complications.

D. Procedural Issues

Although no rigid protocol is applicable to all laboratories, certain procedural issues are worthy of comment. Patient preparation generally entails premedication with mild sedatives. During the procedure a conscious-sedation protocol should be followed.

Patients with contrast allergies should receive nonionic contrast and should be premedicated with steroids. Many laboratories also use antihistamines.

Patients with renal insufficiency should be adequately hydrated before and after the procedure. A minimal amount of radiographic contrast should be used along with biplane angiography when available. There is suggestive evidence that nonionic radiographic contrast may help reduce the incidence of nephrotoxicity. Initial studies using pretreatment with acetylcysteine are very promising for the prevention of nephrotoxicity.

Fasting patients with diabetes mellitus should receive a reduced dose of insulin on the morning of the procedure. Diabetic patients treated with metformin who have mild renal insufficiency rarely have been reported to develop profound lactic acidosis after receiving radiographic contrast. Therefore, the metformin dose should be withheld on the day of the procedure and not restarted until the creatinine is stable, usually 48 h after the procedure. Antiplatelet drugs need not be withheld before cardiac catheterization. Warfarin generally is discontinued until the international normalized ratio (INR) is <1.8. It can be reversed if necessary with vitamin K or fresh frozen plasma. Patients often undergo cardiac catheterization while receiving heparin therapy. In-laboratory activated clotting time (ACT) should be in the range of 300 s (200 to 250 s if glycoprotein IIb/IIIa inhibitors are used) during the procedure and <175 s when the catheters are removed.

Sterile preparation is mandatory for all vascular access sites. It is important for operators to wear masks, caps, and eye protection to prevent accidental operator contamination with blood.

Routine catheterizations of the right side of the heart should not be performed during diagnostic or interventional cardiac catheterizations unless specific information of clinical importance is being sought. Routine use of temporary pacemakers is also inappropriate. In an era of high-quality echocardiographic methods for assessing left ventricular function and valvular gradients, there is only an extremely rare indication for direct left ventricular puncture.

Certain provocative agents may be useful during adult cardiac catheterization. These include (1) fluid loading to assess the hemodynamics associated with constrictive pericarditis or restrictive myocardial disease; (2) the use of afterload alteration or inotropic agents to assess maximal intraventricular gradients in hypertrophic cardiomyopathy or in patients with aortic stenosis and low output and low gradient; (3) the use of coronary vasoactive agents (especially in combination with coronary flow, pressure, or velocity measures); (4) the administration of pulmonary vasodilators in patients with elevated pulmonary vascular resistance; and (5) exercise during the procedure to assess cardiovascular hemodynamics during stress.

Proper procedural technique includes adequate injection of the coronary arteries and the use of multiple orthogonal views with appropriate radiographic angulation for visualization of the various cardiac structures. Pressure measurement requires attention to proper electrical filtering and patient respiration. Accurate measurement of cardiac output is difficult in the best of settings, and the vagaries inherent in all the available methods should be understood to interpret the results properly.

Postprocedural hemostasis is achievable by a variety of means, including manual methods, mechanical compression devices, and percutaneous closure devices. It is important to monitor the hematoma and pseudoaneurysm rate involving each method and each device used in any laboratory.

Catheterization reports should contain certain basic information, and the actual images should be kept for at least 7 years after the study.

E. Personnel Issues

Attending physicians should be credentialed according to local standards. The laboratory director should have extensive experience (>500 procedures performed over his or her career). If interventional procedures are performed in the laboratory, the director should be board certified in interventional cardiology.

The patient consent form should note if any designees other than the attending physician are participating in the procedure. Cardiology trainees (fellows) may be primary operators with supervision. Physician extenders (physician's assistants and nurse practitioners) can participate in cardiac catheterization procedures along with the attending physician, but they cannot be primary operators, and all clinical decision making must reside with credentialed physician operators.

Other cardiac catheterization personnel include nurse practitioners, nursing personnel, radiological or physiological technologists, and now both darkroom (if cinefilm is used) and computer specialists. All are critical professionals and should be treated as such. Continuing education should be provided for nonphysician staff.

F. Ethical Concerns

Ethical concerns include those related both to clinical practice and to biomedical research. Rarely do interventional procedures require 2 cardiologists to be in attendance. Cardiologists should never receive an admission fee, referral fee, or other “kickback” for referring a patient to a facility; this is illegal. Collusion in fixing fees is illegal as well. Unnecessary services should never be performed or billed. Cardiologists must avoid any financial business or industry arrangements that might influence their decision to care for patients because of personal gain ⁽⁵⁾. Receipt of direct remuneration from device, catheter, or drug companies to use such products is a conflict of interest and should be avoided. Procedural information should always be presented honestly, and the collection of procedural outcome data should be systematic and standardized. Informed consent should note all participants in the procedure (physician and physician extenders) and should describe all possible procedures (including ad hoc intervention) should they become a consideration. Clinical research studies require special attention, with patient safety always overriding other aspects of any investigational protocol.

G. Imaging Equipment Issues

Radiographic equipment is now evolving after years of relatively little real change. X-ray tubes with high heat capacities have become commonplace. Image intensifiers have continued to improve, with better conversion factors, improved contrast ratios, less distortion, and better resultant spatial resolution. Image intensifiers optimized for coronary angiography may not be optimal for peripheral vascular imaging. Newer x-ray detectors, such as the flat panel devices, are being investigated as an alternative to the current image intensifier. Video cameras are slowly evolving from the standard 525 X 525 lines per video frame to 1023 or 1049 lines with accompanying higher resolution. The video “pickup tube” is also being replaced by charge-coupled devices (CCDs) in many systems.

Nearly all new x-ray equipment that is commercially available allows for digital angiography as cinefilm is gradually phased out. This process should be completed within the next decade. Elimination of cinefilm has many advantages, including the use of lower framing rates, freeze frames for roadmapping, immediate availability of images for final interpretation, improved image playback during the procedure, and elimination of film development, display, and storage problems. Elimination of cinefilm does not reduce the x-ray exposure per frame by much, however, as the primary source of quantum noise is in the x-ray system itself. Digital systems can reduce x-ray exposure and usage by reducing framing rates. Pulsing the fluoroscopic dose helps reduce overall x-ray exposure.

Although the DICOM (Digital Imaging and COmmunication in Medicine) standard has allowed for an acceptable format and media (the CD-ROM) for exchange of information between and among cardiac catheterization laboratories, there is still no uniform standard for short-, near-, and long-term storage. Many archival options are still being evaluated. One limitation that older laboratories face is the availability of an adequate interface that will write the DICOM standard from x-ray acquisition devices to storage and retrieval devices. Most digital cardiac systems incorporate resolutions of 512 X 512 X 8-bit deep images with the capability of acquiring 30 frames per second. This results in a minimal spatial resolution in the order of 0.2 to 0.3 mm. Higher matrices such as 1024 X 1024 can deliver resolutions of up to 0.1 to 0.15 mm but at a marked increase in cost related to data acquisition, storage, and transmission requirements.

Data compression allows for more rapid transmission of images over lower bandwidth lines and requires less storage capacity. Although this is acceptable for many purposes, clinical errors can occur if lossy compression is used. Preliminary results from the multicenter clinical study sponsored by the American College of Cardiology and the European Society of Cardiology suggests that only lossless compression (about 2:1 JPEG compression, for instance) should be used for permanent storage of data and clinical decision making. Higher compression of images may be used for nonclinical situations and certain teaching and demonstrative displays of information.

Digital imaging allows for a practical approach to telemedicine and for the widespread use of quantitative angiographic methods. Further DICOM developments will include standardized formats for physiological data such as hemodynamic and electrocardiographic (ECG) waveforms and patient record demographic and other information. Other modalities such as other radiographic procedures and intravascular ultrasound will eventually be incorporated into the standard.

H. Radiation Safety

The use of ALARA—“as low as reasonably achievable”—doses of x-ray radiation is important. Radiation exposure may be expressed in terms of rems. Radiation injury is defined by either stochastic effects (DNA injury) or nonstochastic effects (cellular injury). The average background radiation exposure is about 0.1 rem per year. Interventional cardiologists receive another 0.004 to 0.016 rem per case. The maximum recommended exposure by the National Council on Radiation Protection and Measurement (NCRPM) is 5 rems per year for the total body. Over an individual's lifetime, the accumulated maximum dose should be no greater than the accumulated rem exposure x age (or a maximum of 50 rems).

The risk of fatal cancer in the United States is about 20%. The additional risk from radiation exposure in the cardiac catheterization laboratory is about 0.04% x total cumulative rem exposure. Pregnant workers can continue to work in the cardiac catheterization laboratory if they so choose. Fetal exposure, as measured by a waist dosimeter, should be no more than 0.05 rem per month or <0.5 rem for the entire pregnancy.

Radiation exposure is measured by either x-ray film badges or transluminescent dosimeter (TLD) badges. It is recommended that these badges be worn on both the thyroid collar and under the lead apron at the waist. Ring dosimeters are rarely worn in the cardiac catheterization laboratory, even though hand exposure may be high.

X-ray scatter is reduced by minimizing the number of magnified views, using digital-only cine runs, keeping the image intensifier as close to the patient as possible, and selecting the highest kilovolt level that provides acceptable image contrast (to reduce the milliamperes generated). Most of the radiation exposure during interventional procedures comes from the extended use of fluoroscopy rather than the brief cine runs. The closer the operator is to the x-ray tube, the greater the radiation exposure (left anterior oblique [LAO] cranial views may result in up to 6 times more radiation than right anterior oblique [RAO] caudal views, for instance). Proper collimation and shielding is important to help reduce exposure. To minimize patient exposure to scatter radiation, the same rules apply, with further efforts to reduce the x-ray dose most important.

I. Special Concerns for the Pediatric Catheterization Laboratory

The goals in the pediatric cardiac catheterization laboratory are to define internal cardiac and vascular structures and hemodynamics. Shunts frequently require evaluation. In recent years the pediatric catheterization laboratory has become as much a therapeutic arena as a diagnostic one, with atrial septostomy, valve and vessel dilation, and stent implantation available. In some institutions, closure of intracardiac defects such as patent ductus arteriosus or atrial septal defect may be accomplished.

A pediatric cardiologist should be responsible for invasive evaluation of patients from birth to 18 years of age. Adult patients with congenital heart disease may be studied by a pediatric cardiologist, a team of adult and pediatric cardiologists working together, or an adult cardiologist with specialized training and interest in adult congenital heart disease. Complication rates in the pediatric cardiac catheterization laboratory tend to be higher than those in adult laboratories. Overall complications are about 8.8%, with major complications about 2%. Neonatal patients and those undergoing interventional procedures are at greatest risk. Informed consent is usually obtained from parents or guardians. Many diagnostic procedures can be done on an outpatient basis, although this may not be practical for a variety of reasons. Eligibility for early discharge after cardiac catheterization must consider the child's age and size, patient or parent reliability, travel time and distance, duration of procedure, time of completion, cardiac physiology, and loss of blood. Overnight observation is often required to ensure safety.

Procedural issues in the pediatric laboratory include the use of deep sedation and even general anesthesia. Vascular access may be decidedly more challenging, although venous-only catheterization may be performed when there is an interatrial communication or by use of transseptal techniques. Biplane angiography is also more important to help visualize the cardiac structures adequately, to recognize catheter positions, and to help reduce the total radiographic contrast dosage. Heart rates in children are generally much higher than in adults, requiring higher framing rates for image acquisition (often 30 to 60 frames per second). Higher injection rates (up to 40 mL per second) are also useful to help define abnormal intracardiac anatomy.

The laboratory should perform a minimum of 75 pediatric cases per year. Generally, an individual cardiologist should perform at least 50 cases per year to maintain skills and reduce risk of complications. A detailed QA plan should be operative. The number of “normal” cardiac catheterizations should be zero.

Oximetry rather than indocyanine green dye methods is now used in shunt measurements. In pediatric cardiac catheterization laboratories, specialized staff should be available to ensure familiarity with the procedures performed.