Cardiovascular Performance Assessment

OVERVIEW

• Summary of cardiovascular performance assessment, primarily in the peri-operative setting

12 LEAD ECG

• easy, quick & cheap
• patient not stressed
• many patients with underlying IHD may have normal resting ECG’s
• may pick up conduction problems or arrhythmia’s

EXERCISE STRESS TEST

• patient must be ambulatory
• estimates functional capacity + ischaemia under stress
• ST depression, hypotension, tachyarrhythmias
• can’t use in patients who can’t ambulate or those who have pre-existing ECG abnormalities (resting ST abnormalities, paced ventricular rhythms, LBBB, ventricular hypertrophy/strain, on digoxin)
• limited by false positives in low risk patients

CARDIAC RADIONUCLEOTIDE IMAGING — SINGLE PHOTON EMISSION COMPUTED TOMOGRAPHY (SPECT) MYOCARDIAL PERFUSION IMAGING

• uses radioactive traces to provide information about regional blood flow, coronary artery perfusion and ventricular function.
• non-perfused myocardium shows up as permanent perfusion defects
• concentrates in tissues in proportion to desmoplastic, metabolic activity and blood flow.
• can use thallium or tecnitium (MYOVIEW) as tracers
• stress can be applied with:
  (1) exercise – detection of 50% or more stenosis -> sensitivity 87%, specificity 73%
  (2) pharmacologically (adenosine or dipyridamole) -> sensitivity 89%, specificity 75%
• improved accuracy with ECG gated SPECT imaging (specificity increases to 90%) -> image data acquired in synchrony with the ECG signal which facilitates evaluation of wall motion and ejection fraction.
• Technetium injected IV -> accumulates in myocardium in proportion to blood flow
• can be injected at presentation of chest pain -> can perform scan within 4 hours with results that can effect morbidity and mortality
• multiple ventricular images are obtained during different phase of cardiac cycle (rest vs exercise)
• the occurrence of regional wall motion abnormalities and the inability to increase LVEF during exercise are suggestive of myocardial ischaemia
• provides prognostic information -> a normal scan @ peak stress is associated with excellent outcome and a cardiac event rate of <1%/year. Echocardiography – excellent images of heart and great vessels, regional and global left and right ventricular function. – versatile and least expensive – can be performed with exercise or dobutamine

DOBUTAMINE STRESS ECHOCARDIOGRAPHY

• utilizes an increasing dose of dobutamine (max 40mcg/kg/min) with simultaneous 2D precordial echocardiography
• looks for new or worsening wall motion abnormalities as an indicator of impaired perfusion, left ventricular systolic or diastolic dysfunction, valvular heart disease
• limited by habitus
• very complex and time consuming test
• very operator dependent

CARDIAC CT CORONARY CALCIUM SCORING

• detects and quantifies the amount of coronary artery calcium (marker of CAD burden)
• approximates total atherosclerotic plaque burden -> strongly predictive of future cardiac events.
• lack of supportive evidence for widespread use but may have a role in screening

CT ANGIOGRAPHY

• non-invasive acquisition of very high-quality coronary CT angiography
• downside = very high radiation exposure, contrast administration, need HR @ 60/min or less

CARDIAC MAGNETIC RESONANCE IMAGING (MRI)

• non-invasive technique for evaluating right and left ventricular function, cardiac masses, congenital heart disease, identification of patient with suspected arrhymogenic right ventricular dysplasia.
• evaluates CAD in many ways -> direct visualization of coronary stenoses, determination of flow within coronaries, evaluation of myocardial perfusion and metabolism, assessment of abnormal wall motion during stress, identification of infarcted and viable myocardium, can detect high-grade CAD and severity of valvular disease.
• downsides – can’t use if patient has metalware insitu or claustrophobic

CORONARY ANGIOGRAPHY

• invasive but can provide definitive treatment
• considered the ‘gold standard’ for evaluating cardiac disease
• provides accurate assessment of coronary vasculature, ventricular function, haemodynamics and anatomy
• remember -> is lumenography only

CARDIOPULMONARY EXERCISE TESTING

• performed on a bicycle ergometer, arm crank or treadmill
• using respiratory gas analysis + ECG
• under exercise conditions oxygen consumption is a linear function of cardiac output -> thus aerobic activity is a surrogate measurement of ventricular function
• >11mL/kg/min -> used to predict mortality of major abdominal operations accurately