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Cardiovascular Testing

J.B. Handler, M.D.Physician Assistant ProgramUniversity of New England

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Abbreviations PCI- percutaneous coronary

intervention CHD- coronary heart disease CABG- coronary artery

bypass surgery Tc- technetium CO- cardiac output SVR- systemic vascular

resistance

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Ambulatory Monitoring Arrhythmia Detection Evaluation of Syncope Evaluation of symptoms suggestive

of arrhythmia Identifying patients with heart

disease at risk for sudden death Evaluation of anti-arrhythmia

therapy

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Ambulatory Monitoring AKA “Holtor Monitoring”: 2 ECG

leads are monitored and recorded by a device (cassette recorder) that patient wears for extended period of time. Provides continuous recording of ECG for 24 hours. Useful for detection of cardiac arrhythmias and determination if their presence correlates with patient symptoms.

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Ambulatory Monitoring Patient diary of symptoms Analysis by both computer and

cardiologist Event Recorders: prolonged

monitoring for months or more. Useful in identifying rhythms that occur

when patient is experiencing symptoms- palpitations, lightheadedness, etc.

Arrhythmia Detection

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Stress Testing: Indications Evaluation of patients with chest

discomfort suggestive of angina pectoris (coronary heart disease).

Assessment of functional capacity in patients with documented CHD. Determine prognosis in high risk subsets.

Screening of high risk individuals with atypical symptoms.

Assess response to therapy including meds, PCI and CABG.

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Stress Testing: Indications Evaluate patients with recent MI pre

and post discharge. Exercise prescription for cardiac

rehabilitation post MI. Screen patients with cardiac risk

factors and certain occupations (pilots, bus and truck drivers, police officers, firemen).

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Physiology of Ischemia Coronary blood flow- oxygen to

myocardium. Exercise increases CO and coronary flow

up to 5x. Blood flow through obstructed arteries

unable to increase to meet demands: ischemia to tissue chest discomfortECG or imaging changes.

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Physiology of Exercise Exercise increases CO and coronary blood

flow. MET: Metabolic equivalents

1 met: resting O2 consumption= 3.5ml/min/kg.

Method: Treadmill testing most commonly used. Provides graded exercise/workloads (METs) and O2 consumption.

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Evaluation of Ischemia Electrocardiogram alone (Stress

Electrocardiography) Nuclear (isotope) imaging + ECG

Thallium201, Tc99 labeled Sestamibi Echocardiography (imaging) + ECG ECG + imaging improves

sensitivity/specificity

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Options for Stress Exercise using motorized treadmills

Protocols using increasing speed/elevation reproduce quantifiable workloads at fixed intervals.

Pharmacologic stress Adenosine and Dipyridamole Dobutamine Utilize ECG + imaging

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Goals of Exercise Testing Increase heart rate and workload in

incremental, objective fashion. Endpoints:

Reproduce symptoms and/or diagnostic evidence of ischemia (ECG).

Achieve target heart rate: 85-90% of PMHR if no ischemic changes.

Dangerous arrhythmias Abnormal hemodynamics: ing BP during

exercise means stop the test!

Exercise Protocols

Exercise Stress Testing

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Stress Electrocardiography Sensitivity overall: 60-70%

Single vessel CAD: 50% 2 vessel CAD: 65% 3 vessel CAD: 85%

Specificity 80-85% For patients without symptoms/ECG

changes, need to achieve 85-90% PMHR before concluding “negative test for ischemia.”

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Stress Electrocardiography in Women High incidence of false positives

in young, healthy women, no risk factors and atypical types of chest pain.

Decreased sensitivity in women with documented CHD.

Consider stress testing with imaging.

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Stress Testing with Nuclear Imaging Isotope (Thallium201 or Tc99sestamibi)

distributes to myocardium via blood flow and intact cell membrane Na/K pump.

Resting tissue (imaged before or several hours after stress) takes up isotope normally as perfusion is adequate at rest.

Ischemic tissue (stress induced) beyond coronary stenosis does not take up isotope intracellulary- appears as “defect” on scan.

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Stress Testing with Nuclear Imaging Resting images compared with

stress images looking for reversible ischemia.

Nuclear scans will also show areas of prior infarction if present: Defect on both resting and stress images.

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Stress Echocardiography Myocardium with normal perfusion

contracts normally, well defined using ultrasound. Heart normally gets smaller, with increased EF during exercise/dobutamine stress.

Ischemic segments (that correlate with coronary artery that is obstructed) have decreased or absent contraction. If multiple or large, heart gets bigger, EF

Stress Echo

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Pharmacologic Stress Testing Dobutamine + Echocardiography Dipyridamole + Nuclear imaging Adenosine + Nuclear imaging Always combine ECG with imaging

Nuclear Isotope: Tc99 Sestamibi or Thallium201

Echocardiography

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Stress Testing + Imaging Clearly superior to stress testing

with ECG alone Increases sensitivity to 85-90% Increases specificity to 90% Similar S/S with both exercise and

pharmacologic stress + imaging Drawback is cost

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Limitations of ECG for Ischemia LVH LBBB Digoxin WPW abnormality In patients with above, must use

imaging when considering stress testing; ECG alone is worthless.

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Echocardiography Non-invasive test, combines 2-D with

doppler ultrasound to image the cardiac chambers, aorta, valves, myocardium, pericardium and blood flow.

Transthoracic vs TEE Global and segmental LV function and EF Hypertrophy, chamber enlargement Detection of endocarditis TEE

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Echocardiography Evaluation of Heart Failure Valvular stenosis, insufficiency Congenital defects, shunting Pericardial disease/effusions Prosthetic valves Ventricular or atrial thrombus

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Radionuclide Ventriculography Isotope (Tc99) used to label RBC’s.

Passage of RBC’s over hundreds of cycles allows reconstruction of the beating heart.

Excellent for evaluation of EF Some value in detecting wall motion

abnormalities. Echocardiography provides more

information and has replaced need for radionuclide ventriculography in most settings.

Radionuclide Angiography

Cardiac Catheterization

AllRefer HealthImages.google.com

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Rt Heart Catheterization Invasive procedure with risk Catheter advanced from central vein into RA,

RV, PA and PCW positions. Pressures obtained. Oximetry performed if congenital heart disease suspected. PCW=LA=LVEDP if MV normal

Measurement of cardiac output and SVR Invasive monitoring of critically ill

patients. Complications: Pneumothorax, arterial

puncture, infection, thrombosis.

Right Heart Pressures

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Lt Heart Catheterization Catheter advanced from major artery into

aorta, across Ao valve into LV; invasive. Pressures recorded: Identify AS, MS Angiography: Contrast (dye) can be

injected into: LV to assess contractility and look for mitral

valve regurgitation. Coronary arteries to identify and define

presence/absence of stenosis/occlusions. Complications: Death, stroke, bleeding,

arterial thrombosis/emboli.

Aortic Pressure

LV Pressure