High-Risk Cardiac Catheterization

8 High-Risk Cardiac Catheterization

Since its inception, heart catheterization has evolved from a diagnostic modality used for hemodynamic assessment and visualization of the coronary anatomy and ventricular function to a therapeutic means to treat pathology, from atherosclerosis to congenital heart defects. More than 1.5 million catheterizations are performed in the United States each year. Complication rates for diagnostic procedures in the catheterization laboratory principally include death, myocardial infarction, stroke, vascular complications, contrast reactions, or arrhythmia. The rates for these complications are very low and have not changed over the past decade (Table 8-1). As the procedure continues to mature, a comfort level has developed in performing procedures on higher risk patients. It is becoming more common for patients to undergo multivessel (including left main) percutaneous coronary intervention (PCI) with hemodynamic support as an elective procedure within most catheterization laboratories.

Table 8-1 Risk of Cardiac Catheterization and Coronary Angiography

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

Adapted from Scanlon PJ, Faxon DP, Audet AM, et al: ACC/AHA guidelines for coronary angiography: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee on Coronary Angiography), JACC 33:1760, 1999.

High-Risk Patient: Definition

Patients classified as high risk are more likely to die or have myocardial infarction or ventricular fibrillation during cardiac catheterization than are other patients. Numerous studies have summarized the clinical and anatomic characteristics of patients at high risk: patients with known significant three-vessel or left main coronary artery disease, severe left ventricular (LV) dysfunction, diabetes, existing arrhythmias, or poorly controlled hypertension (Table 8-2). Patients with high-risk features from stress testing, including ventricular dilatation with stress and a large amount of ischemia myocardium, are at higher risk secondary to the higher likelihood of these patients to have multivessel or left main coronary disease. Patients with congestive heart failure, recent acute myocardial infarction, unstable angina, and severe valvular heart disease (especially critical aortic stenosis) have a high incidence of morbidity and mortality during and after cardiac catheterization. The occurrence of major complications in the cardiac catheterization laboratory has increased with the increasing complexity of interventional procedures.

Table 8-2 Variables Increasing the Risk of Cardiac Catheterization and Coronary Angiography

Anatomic Clinical
  Acute myocardial Infarction ± cardiogenic shock
Left main coronary disease Atrial/ventricular arrhythmias
Three-vessel obstructive disease Poorly controlled hypertension
  Decompensated heart failure (especially NYHA class IV)
Severe valvular disease (especially severe aortic stenosis) Diabetes mellitus
Severe left ventricular dysfunction (EF <30%) Renal insufficiency
  Pulmonary disease (COPD, asthma, OSA)
Severe peripheral vascular disease (vascular access difficulty is also included) Anemia ± bleeding diathesis, active GI bleeding, elevated INR, thrombocytopenia
  Cerebrovascular disease
Saphenous vein grafts IV contrast allergy
Females (?) Age >60 yr or <1 yr
Very small or very large body habitus

  Emergent procedure

COPD, Chronic obstructive pulmonary disease; EF, ejection fraction; GI, gastrointestinal; INR, international normalized ratio; IV, intravenous; NYHA, New York Heart Association; OSA, obstructive sleep apnea.

Prevention of Complications

Meticulous attention to the precatheterization patient assessment and recognition of potential risks decreases procedure-related complications.

Patient Medications

Many medications may affect the patient’s catheterization risk (Table 8-3).

Table 8-3 Medications That May Impact Cardiac Catheterization Risk

Insulin (especially long acting)
ACE inhibitors (lisinopril, ramipril, enalapril)
ARBs (losartan, candesartan)
NSAIDs (ibuprofen, naproxen)

ACE, Angiotensin-converting enzyme; ARBs, angiotensin receptor blockers; NSAIDs, nonsteroidal antiinflammatory drugs.

Warfarin should be held for at least 72 hours before the procedure. The goal international normalized ratio (INR) should be achieving an INR of less than 1.5 before the procedure to reduce the bleeding risk. Understanding why the patient has been taking warfarin is important as he or she may require bridging therapy with heparin, particularly if a mechanical valve is involved.

Diuretics should generally not be taken the morning of the procedure. Dehydration may decrease renal flow and increase the risk of contrast nephropathy and hypotension.

Diabetic patients should not take any short-acting insulin on the morning of the procedure and decrease their long-acting insulin dose by half to help reduce the risk of hypoglycemia. Metformin poses a slight but very real risk of lactic acidosis. Because of this, Metformin should be held for at least 24 hours before the procedure and one should consider holding for 48 hours in those with renal insufficiency. This medication can be restarted 48 hours after the procedure if there is no evidence of decrement in renal function. Other oral diabetic medications may also need to be held.

Because of sedation during the procedure, it is difficult to monitor the diabetic patient for signs/symptoms of hypoglycemia or hyperglycemia. One should check blood sugar before initiation of the procedure and as needed throughout the case to minimize risk. If appropriate, the patient should have a dextrose or insulin infusion maintained during the periprocedure period in an attempt to avoid hypoglycemia or hyperglycemia.

Erectile dysfunction medications can also cause significant harm in the catheterization laboratory. When combined with nitrate therapy, there can be a precipitous drop in blood pressure that does not respond well to volume or vasopressor resuscitation. Therefore sildenafil (Viagra) and vardenafil (Levitra) should be held for a minimum of 24 hours before the procedure. Tadalafil (Cialis) has a half-life of 17.5 hours and must be held for 4 days before the procedure.

Radiographic Contrast Media

The use of iodinated contrast must always be considered a potential source of complications in patients undergoing catheterization. There are multiple contrast agents currently available, and differentiating between them requires knowledge of their characteristics (see Chapter 4) and recognition of their chemical and trade names. Low osmolar and nonionic contrast agents are associated with a lower incidence of bradycardia, hypotension, and myocardial ischemia developing in the patient, and these agents are now routinely used during cardiac catheterizations. Almost all cardiac catheterizations today are routinely performed with nonionic, low-osmolality agents.

Contrast-induced renal insufficiency represents the leading cause of in-hospital acute renal failure and is discussed in detail in Chapter 4. Several risk factors have been identified that are found in patients at higher likelihood of developing contrast-induced nephropathy (CIN) (Table 8-4). Unfortunately, many of these parameters are not changeable and therefore do not lend themselves as potential ways to avoid CIN. A risk score has been devised identify patients at higher risk for CIN and is shown in Figure 8-1. Prophylactic strategies to decrease the risk of CIN center around three strategies: maintaining adequate intravascular volume, limiting the amount of contrast delivered, and avoiding medications that could exacerbate renal dysfunction.

Table 8-4 Risk Factors for Development of Contrast-Induced Nephropathy

Patient Related Extrinsic Possible
Existing renal insufficiency (est GFR <60/ml/min/1.73 m2) Contrast volume administered Metabolic syndrome
Congestive heart failure High osmolal contrast Diabetes
Diabetes with existing renal insuff. Intraaortic balloon pump used Impaired glucose tolerance
Age >70 yr Nephrotoxic drugs Hyperuricemia
Volume depletion Multiple contrast administrations (within 72 hr) ACEi or ARB
Hypotension Urgent/emergent PCI Female gender
Anemia   Multiple myeloma
Hypertension   Cirrhosis
Peripheral vascular disease    

ACEi, Angiotensin-converting enzyme inhibitor; ARB, angiotensin receptor blocker; est, estimated; GFR, glomerular filtration rate; insuf., insufficiency; PCI, percutaneous coronary intervention.

Modified from Klein et al, The use of radiographic contrast media during PCI: A focused review. Cathet Cardiovasc Intervent 2009; 74:728.

There are many protocols that have been published that outline how to ensure adequate hydration. The most commonly cited formula uses 0.9% normal saline for 12 hours before and 12 hours after the procedure. Sodium bicarbonate for hydration also is commonly used (154 ml of 1000 mEq/L sodium bicarbonate to 846 ml of 5% dextrose with an initial intravenous (IV) bolus of 3 ml/kg per hour for 1 hour immediately before contrast followed by a rate of 1 ml/kg per hour during the contrast exposure and for 6 hours after the procedure). Data supporting the use of acetylcysteine (600 mg orally twice daily the day before and day of the procedure), although modest, suggest that it can be considered for patients at high risk of contrast nephropathy. Many other pharmacologic treatments (including furosemide, mannitol, dopamine, and fenoldopam) have not been shown to be effective or even have caused more harm and should not be used.

To minimize the chance of CIN, use the lowest amount of IV contrast necessary to perform the study. Whether the iso-osmolar or low-osmolar agents reduce CIN remains under study.

Medications such as angiotensin receptor blockers (ARBs), angiotensin-converting enzyme inhibitors (ACEi), and nonsteroidal antiinflammatory drugs (NSAIDs) should be discontinued for 1 to 2 days before a catheterization. Withholding them for 3 to 4 days following the procedure is also commonly done. However, it has never been shown that the use of ACEi or ARBs in the absence of renal artery stenosis truly increases the risk of renal insufficiency.

Allergic reactions to contrast are discussed in Chapter 1. It is worth remembering that these reactions are characterized as “anaphylactoid” in that they do not require previous exposure to contrast (and thus circulating IgE) to exist but do occur as a result of mast cell degranulation. A patient with a history of multiple food and drug allergies and, of course, those that have had previous reactions to contrast are especially at high risk. The perception that patients having a seafood or shellfish allergy also are at higher risk has never been shown to be true and should not be used as criteria to administer prophylaxis for contrast reactions.

Prophylaxis for patients who are at risk for reactions to contrast media should include prednisone and diphenhydramine. Figure 8-2 depicts treatment algorithms for mild and severe reactions.

{Fig. 8-3}

Management of Complications During Cardiac Catheterization

Complications of coronary arteriography in high-risk patients must be managed at once (Table 8-5).

Table 8-5 Management of Complications During Cardiac Catheterization

Complications and Precautions Treatment
Ventricular tachycardia, asystole, or fibrillations (0.6%) Use nonionic contrast agents in high-risk patients
  Cough for temporary increase in BP
  Remove catheter from RV, LV, or coronary ostium
  Do not wedge coronary artery catheter; contrast material washout should be brisk; ECG and BP should be normal before next injection
  CPR followed by prompt defibrillation (200J)
  Do not inject when catheter tip pressure is damped
  Lidocaine (50 mg bolus, 2 to 4 mg/min IV)
  Use atropine, volume expansion, or infusion
  Amiodarone (300 mg bolus) then metaraminol (Aramine) for hypotension
  Refractory VF usually as a result of extensive CAD; emergency percutaneous cardiopulmonary bypass should be considered
  Limit contrast medium injected into coronary arteries; avoid prolonged injections
Air embolism (0.1%) Prevention: careful back bleeding and flushing of all connections. Make sure all connections tight.
  Treatment: 100% oxygen,fluids, aspiration, ACLS if indicated.
Hematoma in femoral artery (0.1% major, 1% to 2% minor) Puncture below inguinal ligament inferior epigastric artery and above bifurcation of superficial and profunda femotal arteries
  Evacuation rarely required
  Attention to compression
  Surgical consult for enlarging hematoma, compartment syndrome, or cool extremity
  Prolonged compression if patient coughing, or has aortic insufficiency, hypertension, or heparin not reversed
  Vascular closure device
Retroperitoneal bleeding Avoid high (above IEA) femoral artery puncture
  Reverse anticoagulants
  Volume replacement
  Watch for hypotension, low abdominal or flank pain within 2-12 hr of procedure. Low hematocrit, tachycardia (if not receiving beta-blockers)
  Transfusion if hematocrit <25
  Surgical consultation
  CT scan

BP, Blood pressure; CAD, coronary artery disease; CPR, cardiopulmonary resuscitation; CT, computed tomography; ECG, electrocardiogram; IEA, inferior epigastric artery; IV, intravenous; LV, left ventricle; RV, right ventricle; VF, ventricular fibrillation.

Vascular Complications

Causes of peripheral arterial complications should be identified early. If a large dissection or thrombotic occlusion occurs, a vascular surgeon should be consulted immediately or, alternatively, access can be obtained in the contralateral femoral artery and the dissection may be treated percutaneously (i.e., stenting).

Enlarging hematomas should be given prompt attention because they may result in neurovascular compromise to the leg. Direct pressure usually is sufficient to obtain hemostasis, but sometimes patients need to be brought back to the laboratory. To tamponade the bleeding site, a balloon may be inflated in the area of the femoral artery where contrast is leaking from the vessel. In some cases, the placement of a covered stent to ensure hemostasis of the artery is necessary. A vascular surgeon typically will be able to identify the defect in the artery and achieve hemostasis in the operating room.

Arterial thromboembolism to other areas, such as the brain, may not be immediately treatable but requires close observation or prolonged heparin, depending on neurologic findings. Occipital blindness, a rare event that is caused by hyperosmolarity of the contrast agent, is usually transient and requires no definitive treatment except for hydration and maintenance of blood pressure. Steroids have also been used to treat this condition.

An air embolus to the central nervous system may cause the patient to show features of acute stroke such as agitation, confusion, or aphasia. A small air embolus usually resolves and does not often result in permanent damage. Although hyperbaric oxygen chambers have been used successfully for treatment, these are not widely available.

Hypotension may occur before, during, and after cardiac catheterization from a variety of conditions. Before cardiac catheterization, hypotension may be caused by hypovolemia induced by fasting before the procedure (water intake should be allowed) or diuretics.

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Jun 4, 2016 | Posted by in CARDIAC SURGERY | Comments Off on High-Risk Cardiac Catheterization

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