For far too long, many patients have undergone a cardiac test that carries grave risks with the misunderstanding that they are getting the definitive assessment of their coronary arteries.
Chances are if you have visited an emergency room in the USA with chest pain and you weren’t clearly having an acute heart attack, you ended up getting one of two tests: a stress test or an invasive coronary angiogram (ICA).
What Is A Cardiac Catheterization?
For decades the ICA (commonly termed “cardiac catheterization or cath”) was considered the “gold standard” for the assessment of the arteries to the heart (the coronary arteries.) This invasive test involves inserting a tube (catheter) into either an artery in the wrist or groin, threading the catheter up the artery to the aorta and injecting contrast dye directly into the coronary arteries.
The x-ray movie images (angiogram) obtained then show the dye within the lumen of the arteries. If the column of dye is impinged upon an obstruction is diagnosed. However, early plaque in the arteries doesn’t necessarily stick into the lumen and typically resides in the wall, hidden from these “lumenograms.”
Below are the freeze-frame images of the left coronary artery invasive angiogram from a man we shall call Jerry who underwent catheterization in his 40s for atypical chest pain. He was told he had normal arteries, that they were “clean”.
Given the news that his arteries had no plaque build-up, he felt no need to modify his lifestyle or take cholesterol medications in order to avoid the fate of early death from myocardial infarction that his father had suffered at age 50.
Limitations Of The Cardiac Cath In Identifying Atherosclerotic Plaque
When I first saw him a year after the cardiac cath I told him that although his previous cardiologist had told him all was fine with his coronary arteries he could, in fact, have significant diffuse subclinical atherosclerosis and still be at high risk for a heart attack.
This came as quite a shock to Jerry as he, like most laypeople, view the cardiac cath as the “gold standard” for assessment of the coronary arteries. For most patients, a normal cath has been viewed as a warranty against heart attack
Although ICA has been the gold standard for the diagnosis of coronary artery disease, lumenography only shows the internal arterial lumen and does not see the vessel wall with its developing atherosclerotic plaque. Previous studies analyzing serial angiograms from patients presenting with acute coronary syndrome (ACS) have suggested that in nearly two-thirds of the culprit lesions, the coronary angiogram obtained a few months before the acute event demonstrated a non-significant stenosis.
Identifying Early Plaque Using Coronary Calcium Scans
I recommended the patient get a coronary artery calcium (CAC) scan to look for early coronary plaque and this demonstrated two small calcific plaques in the proximal portion of his LAD coronary artery. His calcium score was 9 which is higher than 82% of 45-year-old white males.
Now that we had visual proof of the plaque in his arteries he was motivated to change his lifestyle to reduce the risk of suffering his dad’s fate. In addition, he was now willing to take medications to further reduce risk.
A year later he was admitted to our hospital with palpitations and chest tightness. This time as I was his cardiologist we performed a noninvasive test-a coronary CT angiogram (CCTA). This demonstrated the two small areas of calcification in the LAD we had noted on the calcium scan but in addition, we were able to see surrounding those foci of calcification substantial premature build-up of soft plaque.
Following the CCTA and a more definitive assessment of his coronary artery status we were able to tell him there was no significant blockage of the coronaries and therefore no need for any stenting or bypass procedure.
Just as important, however, was the knowledge that he had a substantial plaque in the LAD which puts him at risk for heart attack.
With this knowledge, we were able to convince him to undergo substantial lifestyle changes to reduce his long term risk of heart attack and stroke. In addition, he was started on statin therapy to further reduce those risks.
The CCTA is performed using a special X-ray scanner and the risks are a small amount of radiation plus the risks of administration of intravenous radioiodine contrast. The injected dye material can cause allergic reactions in those predisposed and worsen kidney function in patients with underlying kidney disease.
What Are The Risks of Cardiac Cath?
Patients acquiring information from the website of the American Heart Association would conclude a cath is no big deal:
Cardiac cath is usually very safe. A small number of people have minor problems. Some develop bruises where the catheter had been inserted (puncture site). The contrast dye that makes the arteries show up on X-rays causes some people to feel sick to their stomachs, get itchy or develop hives.
Even the NIH website downplays the risks, terming it a “relatively safe procedure” with rare complications.
However, the procedure is associated with substantial morbidity ranging from internal bleeding requiring surgery to disabling stroke. Although the risk of dying from the procedure has declined over the last 30 years it is still around .05%.
I have included a recent detailed summary of potential complications at the end of this post.
There are definite indications for getting a cardiac catheterization and I refer patients for this procedure on a daily basis. The clearest benefit is in patients presenting with clear evidence for myocardial damage (elevated troponin levels) from a myocardial infarction. In such patients the known benefits of opening tightly blocked coronary arteries outweigh the risks of the procedure.
However, patients should think twice and have an extensive discussion with the cardiologist recommending the test when there has been no evidence for myocardial damage.
Most importantly, patients should know that a declaration of “clean arteries” or “the arteries of a twenty-year-old” from the results of a cardiac cath do not guarantee freedom from cardiac events down the line. To detect early and premature atherosclerotic plaque build-up which corresponds to a very high lifetime risk of heart attack and stroke other techniques that look at the arterial wall and not the lumen are needed.
For the youngish, vascular ultrasound imaging for measurement of carotid IMT and soft plaque detection is useful, whereas CAC or CCTA is more useful in subjects over age 40 years of age.
N.B. As promised a long laundry list of complications for your edification.
The risk of major complications during diagnostic cardiac catheterization procedure is usually less than 1%, and the risk and the risk of mortality of 0.05% for diagnostic procedure. For any patient, the complication rate is dependent on multiple factors and is dependent on the demographics of the patient, vascular anatomy, co-morbid conditions, clinical presentation, the procedure being performed, and the experience of the operator. The complications can be minor as discomfort at the site of catheterization to major ones like death.
But there are very serious complications of the procedure that can result in death or serious disability.
From a recently updated review of cath complications
Local Vascular Complications
These are among the most common complications seen after cardiac catheterization procedures. Hematomas are usually formed following poorly controlled hemostasis post sheath removal. Most hematomas are self-limiting and benign, but large rapidly expanding hematomas can cause hemodynamic instability requiring resuscitation with fluids and blood. The incidence of this complication is significantly reduced in transradial access. In patients with transfemoral access, retroperitoneal bleeding should be suspected if there is a sudden change in the hemodynamic stability of the patient with or without back pain as there may not be any visible swelling in the groin for some of these patients. The incidence of this complication is less than 0.2%. Strong clinical suspicion along with immediate imaging, usually with CT scan, helps make a diagnosis of this problem. Identification of the bleeding source is essential for patients with continued hemodynamic deterioration. These life-threatening bleeds are more frequent when the artery is punctured above the inguinal ligament. Most patients are managed with a reversal of anticoagulation, application of manual compression and volume resuscitation and observation. Patients with continued deterioration with need coiling of the bleeding source vessel, or balloon angioplasty or covered stents for bleeding from larger vessels.
When the hematoma maintains continuity with the lumen of the artery, it results in the formation of a pulsatile mass locally, defined as a pseudoaneurysm. This will be associated with bruit on examination. They happen following low access in the superficial femoral artery as opposed to the common femoral artery. These are usually diagnosed by ultrasound Doppler imaging or CT angiography. Small pseudoaneurysms of the less than 2 to 3 cm in size may heal of spontaneously and can be followed by serial Doppler examinations. Large symptomatic pseudoaneurysms can be treated by either ultrasound-guided compression of the neck of pseudoaneurysm or percutaneous injection of the thrombin using ultrasound guidance or may need surgical intervention.
Direct communication between the arterial and venous puncture sites with ongoing bleeding from the arterial access site leads to the fistula formation and are associated with a thrill or continuous bruit on examination. These usually will require surgical exploration as they are unlikely to heal spontaneously and may expand with time.
This is an infrequent complication and occurs in patients with an increased atherosclerotic burden, tortuous arteries, or traumatic sheath placement. Non-flow limiting dissections usually heal spontaneously following sheath removal. A flow limiting large dissections could lead to acute limb ischemia and should be treated immediately with angioplasty and stenting. Vascular surgery is usually reserved for patients with failed percutaneous techniques.
Thrombosis and Embolism
This complication is extremely rare with the use of the low profile catheters and predisposing factors include small vessel lumen, and associated peripheral arterial disease, diabetes mellitus, female sex, large diameter sheath, and prolonged catheter dwell time. Treatment involves removal of the occlusive sheath, percutaneous thrombectomy in conjunction with vascular surgery consultation.
Vascular Complications after Transradial Access
The most frequent complication after transradial access is about a 5% risk of radial artery occlusion. This is a clinically insignificant complication if the Allen test is normal. Patients with incomplete palmar arch and abnormal Allen test may have symptoms of hand ischemia after radial artery occlusion.
Radial artery spasm is another frequent complication, and this can be avoided by the use of local vasodilatory medications and systemic anxiolytics. Perforation of the radial artery is an extremely rare complication and is usually managed with prolonged external compression and rarely requires vascular surgery intervention.
Other Major Complications
The incidence of death with cardiac catheterization has decreased progressively and is less than 0.05% for diagnostic procedures. Patients with depressed left ventricular systolic function and those presenting with shock in the setting of acute myocardial infarction are at increased risk. In some subsets of patients, the risk of mortality can be more than 1%. Other factors that would increase the risk include old age, the presence of multivessel disease, left main coronary artery disease, or valvular heart disease like severe aortic stenosis.
The reported incidence of periprocedural myocardial infarction for a diagnostic angiography is less than 0.1%. This is mostly influenced by patient-related factors like the extent and severity of underlying coronary artery disease, recent acute coronary syndrome, diabetes requiring insulin, and technique-related factors.
The overall risk of stroke in recently reported series is low at 0.05% to 0.1% in diagnostic procedures and can increase to 0.18% to 0.4% in patients undergoing intervention. This can be a very debilitating complication associated with a high rate of morbidity and mortality. The risk is higher in patients with extensive atherosclerotic plaque in the aorta and aortic arch, complex anatomy, procedures requiring multiple catheter exchanges or excessive catheter manipulation, or the need for large-bore catheters and stiff wires.
Dissection and Perforation of the Great Vessels
Dissection of the aorta, perforation of the cardiac chambers, perforation of the coronary arteries is an extremely rare complication. The risk is higher in procedures with intervention as opposed to diagnostic procedures only. Patients with type A aortic dissection involving the ascending aorta will require surgical correction. Patients with a cardiac chamber or coronary perforation resulting in the accumulation of the blood in the pericardial space will need urgent pericardiocentesis to restore hemodynamic stability and immediate surgical consultation.
Cholesterol emboli from friable vascular plaques can give rise to distal embolization in multiple vascular beds. These are usually recognized by digital discoloration (blue toes), livedo reticularis. This can also manifest as a neurological squeal or renal impairment. The risk of this complication is minimized by exchanging catheters over a long wire and minimizing the catheter exchanges. Retinal artery occlusion causes Hollenhorst plaque.
Allergic reactions can be related to the use of local anesthetic, contrast agents, heparin or other medications used during the procedure. Reactions to the contrast agents can occur in up to 1% of the patients, and people with prior reactions are pretreated with corticosteroids and antihistamines. Use of iso-osmolar agents decreases the risk compared to high osmolar agents. When severe reactions do occur, they are treated similarly to anaphylaxis with intravenous (IV) epinephrine (initial dose 1 ml of 1:10000 epinephrine).
Acute Renal Failure
The incidence of the reported contrast nephropathy is quite variable (range 3.3% to 16.5%) in the patients undergoing cardiac catheterization resulting in a transient increase in the serum creatinine levels after exposure to contrast material. In the National Cardiovascular Data Registry, the incidence of contrast-induced acute kidney injury was 7.1%, among the patients undergoing elective and urgent coronary intervention. The risk is higher in patients with underlying moderate to severe renal disease, people with diabetes, elderly, females, patients on diuretics, ACEI, and metformin. Adequate pre-hydration, use of iso-osmolar agents, and techniques to minimize the amount of dye used will help prevent this complication. Renal atheroemboli can also cause renal failure and are associated with other signs of embolization.
Cardiac catheterization is performed using sterile technique, and local or systemic infection is extremely rare. Routine prophylaxis for endocarditis is not recommended during cardiac catheterization procedures.
Radiation skin injury can occur if a patient is exposed to excessive doses of radiation to one particular area of the body and manifestation could range from mild erythema to deep ulceration. Skin biopsies should be avoided for these lesions as they would make the underlying condition worse. This complication should be managed by a combined team of cardiologists, dermatologists, and plastic surgeons.
The occurrence of the ventricular fibrillation or ventricular tachycardia during the procedure could be related to irritation or ischemia of the myocardium by the catheter, contrast material or occlusive balloons. These arrhythmias occur more frequently in people presenting with acute ST-elevation myocardial infarction and treatment includes cardioversion along with anti arrhythmic drugs and restoration of the flow to the occluded artery. Atrial tachyarrhythmias can occur following the irritation of the right atrium during right heart catheterization and is usually self-limiting.