Cardiac catheterization: Coronary angiogram, intracoronary imaging, and physiology

1

What constitutes cardiac catheterization?

• Cardiac catheterization typically includes the following four procedures: coronary angiogram, left heart catheterization, left ventricular (LV) angiogram, and right heart catheterization.

• Coronary angiogram refers to opacification of coronary arteries with iodinated contrast after selective cannulation using specialized end-hole catheters inserted via peripheral arterial access (usually femoral or radial). These catheters come in a wide variety of preformed shapes to help cannulate coronary arteries and their choice depending upon the access site, coronary “takeoff,” aortic root length, and operator preference. Judkins left and Judkins right catheters are the most commonly used catheters to selectively engage left main and right coronary artery (RCA) ostia, respectively.

• Left heart catheterization refers to the catheter placement (usually with a pigtail catheter) within the LV to record LV systolic and end-diastolic pressures.

• LV angiogram involves contrast injection through a catheter into the LV. While this could give a fair idea of LV systolic function and regional wall motion, most operators are shying away from routinely performing LV angiogram to minimize contrast use and radiation exposure, especially when the same information can be easily obtained from an echocardiogram.

• Right heart catheterization is discussed separately in Chapter 12 .

2

What are the indications for coronary angiogram?

• Although cardiac catheterization is a relatively safe procedure, life-threatening complications can rarely occur, so there needs to be a clearly thought-out and documented indication with a plan for how to use the information obtained for patient management. In most cases, coronary angiography is best reserved for patients who are amenable to and candidates for coronary revascularization and when findings are likely to result in changes to therapy. Prior to proceeding with elective coronary angiogram in patients with stable symptoms, a trial of “optimal medical therapy” is often recommended, which includes the use of two or more maximally tolerated antianginal medications (beta-blockers, calcium channel blockers, long-acting nitrates, and/or ranolazine). Although recommendations are consistently evolving, generally accepted indications for cardiac catheterization for various clinical settings are listed in Table 13.1

  Table 13.1

  Generally Accepted Indications for Diagnostic Cardiac Catheterization

  Diagnosis of Stable Ischemic Heart Disease

  Follow-up of high-risk findings on noninvasive stress testing Patients with unacceptable ischemic symptoms despite optimum medical therapy and who are amenable to and candidates for coronary revascularization Patients with suspected symptomatic CAD who cannot undergo diagnostic stress testing or have indeterminate or nondiagnostic stress test results Unexplained left ventricular systolic dysfunction Stress testing results suggesting multivessel disease and potential survival benefit from revascularization

  Acute Coronary Syndromes

  As part of primary PCI for STEMI As part of early invasive strategy in patients with NSTE-ACS who have moderate- to high-risk features and no contraindications Patients status post STEMI treated with thrombolytic therapy Patients with STEMI who within 36 h of presentation develop hemodynamic or electrical instability

  Post-revascularization

  Recurrent angina within 9 months of percutaneous coronary revascularization Recurrent angina within 12 months of coronary artery bypass grafting Select patients in special professions, such as pilots, due to regulatory issues

  Ventricular Arrhythmias

  Survivors of sudden cardiac death, especially if caused by ventricular tachycardia or ventricular fibrillation Sustained (>30 s) monomorphic ventricular tachycardia or nonsustained (<30 s) polymorphic ventricular tachycardia

  Valvular Heart Disease

  Hemodynamic assessment when the results of echocardiography are indeterminate Preoperative to assess for presence and extent of CAD in middle-aged and older patients who are to undergo open surgical valve replacement/repair Preprocedure to assess for presence and extent of CAD in patients undergoing structural interventions, such as TAVR or MitraClip

  Other Conditions

  Suspected Prinzmetal variant angina Hemodynamic assessment of shunts in patients with congenital heart disease or acquired shunts Survey assessments in cardiac transplants for coronary vasculopathy

  CAD, Coronary artery disease; NSTE-ACS, non–ST-segment elevation acute coronary syndrome; PCI, percutaneous coronary intervention; STEMI, ST-segment elevation myocardial infarction; TAVR, transcatheter aortic valve replacement.

3

What are the potential risks of cardiac catheterization?

• For “all comers,” the risk of any major complication during cardiac catheterization is <1%, and the risk of procedural mortality is approximately 1 in 1000 ( Table 13.2 ). Major complications include the following:

  • Death.

  • Periprocedure stroke.

  • Periprocedure myocardial infarction.

  • Mechanical ventilation.

  • Major vascular complications (retroperitoneal hemorrhage, pseudoaneurysm, and arteriovenous fistula and cholesterol embolus syndrome).

    • Other risks include radiation exposure, contrast-induced nephropathy, local nerve injury, infection, access site hematoma, and contrast reaction. The procedural risks vary according to the individual patient factors as well as the clinical setting. For example, these risks may go up substantially in a patient with acute myocardial infarction and cardiogenic shock, especially if undergoing a high-risk percutaneous coronary intervention (PCI). In general, patient factors that commonly contribute to increased procedural risk include old age, peripheral vascular disease, chronic kidney disease, coagulopathy, and extremes of body mass index. All these potential risks must be explained to the patient as part of the informed consent prior to performing cardiac catheterization.

  Table 13.2

  Complication and Risk During Diagnostic Cardiac Catheterization for “All Comers”

  COMPLICATION	RISK (%)
  Mortality	0.11
  Myocardial infarction	0.05
  Cerebrovascular accident	0.07
  Arrhythmia	0.38
  Vascular complications	0.43
  Contrast reaction	0.37
  Hemodynamic complications	0.26
  Perforation of heart chamber	0.03
  Other complications	0.28
  Total of major complications	1.70

4

Which patients should be premedicated to prevent allergic reactions to iodine-based contrast?

• In patients with a history of prior true allergic reaction (e.g., hives, urticaria, bronchoconstriction) to iodine-based contrast, the risk of repeat anaphylactoid reaction to contrast agents is reported to be 17% to 35%. Such patients should be premedicated before angiography. A common regimen is 50 mg orally (PO) of prednisone taken 13, 7, and 1 hour prior to the procedure and 50 mg oral diphenhydramine an hour prior to the procedure. The 2011 ACCF/AHA/SCAI guidelines do not consider allergy to fish or shellfish an indication for steroid pretreatment.

5

What are the major risk factors for contrast-induced nephropathy (CIN)?

• Preexisting renal disease and diabetes are the two major risk factors for the development of CIN, which typically develops within 48 to 72 hours after contrast exposure. The risk is also related to the amount of iodine-based contrast used during the catheterization procedure. Periprocedure hydration is the single most important proven method of reducing the risk of contrast nephropathy. The 2011 ACCF/AHA/SCAI PCI guidelines suggest a regimen of isotonic crystalloid (e.g., normal saline) 1.0 to 1.5 mL/kg/h for 3 to 12 hours before the procedure and continuing for 6 to 24 hours after the procedure. Intravenous fluid hydration guided by LV end-diastolic pressure has shown positive results. Treatment with N -acetylcysteine does not reduce the risk of contrast nephropathy and is not indicated.

6

How are coronary angiographic projections named?

• Coronary angiography utilizes multiple orthogonal views to evaluate coronary arterial anatomy to decrease the likelihood of missing an eccentric but significant stenosis. By convention, angiographic views are named according to the position of the image intensifier (located above the patient) and degree of angulation denoted. Anteroposterior projection (AP) signifies the position of the image intensifier directly above the patient. Left anterior oblique (LAO) 30-degree angulation means the position of the image intensifier is at 30 degrees to the left of the patient, whereas right anterior oblique (RAO) implies the position of the image intensifier to the right of the patient. Cranial angulation denotes the position of the image intensifier to the head of the patient and vice versa. Native left and right coronary arteries are usually engaged in LAO 30-degree angulation. LAO view helps visualize left- and right-sided segments of any cardiac structure, while RAO view splits it anteriorly and posteriorly. Cranial and caudal angulations can further help in opening up the “hidden” segments. This way, two-dimensional images of fluoroscopy can help tease out the three-dimensional geometry of coronary arteries.