Cath Lab Digest

Abstract

Before patients enter the cardiac cath lab for a procedure, almost all have undergone one or more diagnostic tests, imaging studies, an electrocardiogram (ECG), or blood work such as serum troponin levels to confirm the likelihood of coronary artery disease. Tests and imaging studies include stress tests, echocardiography, nuclear imaging, positron emission tomography (PET), computed tomography angiography (CTA), and magnetic resonance imaging (MRI). These procedures aid in the detection and diagnosis of cardiovascular disease by isolating areas of cardiac pathology, myocardial viability, and likelihood of significant coronary artery disease. When these tests are positive, or suggestive of coronary artery disease, it is important to confirm the diagnosis with a cardiac catheterization. This article will discuss an overview of these non-invasive imaging modalities, their role in detecting cardiac and coronary artery disease, and how the cath lab staff can use this information in daily practice.

Introduction

According to the American Heart Association, approximately 81 million American adults have one or more forms of cardiovascular disease, and 17 million have had a heart attack, angina pectoris or both.¹ Cardiovascular disease is also the leading killer of adult men and women in the United States. Heart attacks account for over 600,000, or 26%, of the annual deaths in the United States, and every year, around 785,000 Americans have a first heart attack.² In this setting, cardiovascular disease management is national healthcare priority, and it is the reason why more tests are performed on the cardiovascular system than any other part of the body. The direct and indirect impact of heart disease on the American economy, including health care expenditures and lost productivity, is estimated to be over 500 billion dollars per year.³ This makes effective use and interpretation of cardiovascular procedures a vital component in containing healthcare costs and effectively diagnosing cardiovascular disease. Over 1 million Americans have an inpatient cardiac catheterization annually, with significant numbers of patients having elective, outpatient catheterizations.⁴ However, the majority of patients who have non-invasive imaging of the heart do not require cardiac catheterization.

Understanding the diagnostic tools that evaluate cardiovascular and coronary artery disease (CAD) provides important benefits for cath lab staff. These tools can indicate areas causing angina and ischemia. They can determine if an area of interest has myocardial viability and can be an important determinant in providing treatment strategies for patients diagnosed with CAD. A positive stress test or ECG change in the inferior wall, for instance, may lead the cardiologist to perform a percutaneous coronary intervention (PCI) on a right coronary lesion or dominant circumflex lesion. This is important if the patient has disease in more than one vessel. Myocardial viability studies such as a nuclear stress test, dobutamine echocardiography, PET scan, or MRI may determine whether a patient is treated with medical therapy, stents, or surgery. This article will survey the major non-invasive cardiac tests and imaging modalities, and aid the cath lab staff in understanding their applications.

Electrocardiogram

Before a patient enters the cardiac cath lab, they will usually undergo a variety of non- or minimally-invasive procedures to make a diagnosis. Some of the most reliable detection tests for the heart are the easiest to perform. The electrocardiogram (ECG) takes a couple of minutes, and provides important data concerning the electrical and mechanical activity of the heart. It is the most important frontline diagnostic tool used in cardiac medicine. It detects a wide variety of disease processes, and is the entry point for activating acute myocardial infarction (MI) protocols. An ECG detects injury and ischemia by looking for ST segment elevations, depressions and T-wave inversions. New onset of left bundle branch blocks and Q wave changes can also be a predictor of a new onset of CAD. The ECG also identifies old infarcts, hypertrophy, atrial fibrillation, tachycardias, bundle branch blocks, and other arrhythmias that are extremely valuable in managing patient outcomes and treating patients in the cardiac cath lab.