Investigations of the Cardiovascular system

Investigations of the Cardiovascular system Electrocardiography Radiology Echocardiography CT imaging MRI Cardiac catheterization Radionuclide imaging

Electrocardiography (ECG) uses: To determine heart rhythm Status of the conducting system To diagnose myocardial ischemia or infarction Chamber enlargement and hypertrophy Effects of drugs & metabolic disorders (electrolyte imbalance, acidosis, etc.)

The ECG Leads Standard leads (Bipolar Leads) Augmented leads Chest leads

Standard leads (Bipolar Leads) Lead I: between left arm & right arm Lead II: between right arm & left leg Lead III: left arm and left leg

Augmented Limb Leads aVR: right arm and central terminal aVL: left arm and central terminal aVF: left foot and neutral central terminal

Chest Leads Six leads: V1-V6 V1 & V2: face the RV V3 & V4: face the septum V5 & V6: face the LV.

Exercise ECG In patients with angina, the resting ECG may be normal The principle of the test is to stress the heart and observe for ECG changes of ischemia ECG and BP are continuously recorded while the patient is exercising on a bicycle or a treadmill

INDICATIONS FOR EXERCISE TESTING: To confirm the diagnosis of angina To evaluate stable angina To assess prognosis following myocardial infarction To assess outcome after coronary revascularisation, e.g. coronary angioplasty To diagnose and evaluate the treatment of exercise-induced arrhythmias

Exercise ECG Positive exercise test: High risk ETT: > 2mm ST segment depression > 1mm ST segment elevation High risk ETT: Low threshold for ischemia Fall in BP during exercise Widespread, marked or prolonged ischemic changes Exercise-induced arrhythmia contraindicated in the presence of unstable angina, decompensated heart failure and severe hypertension and aortic stenosis.

Ambulatory ECG Monitoring (Holter) Continuous recording of ECG over 24 hours or more Used to detect transient episodes of ischemia or arrhythmia which can rarely be captured during routine, ordinary ECG recording

Radiology of the Heart Chest X-ray: Postero-anterior view (PA view): Size of the heart Shape of the heart Specific chamber enlargement Status of the pulmonary circulation

Radiology of the Heart Cardiac size: Cardio-thoracic ratio (CTR): Normally < 0.5 Enlargement of the heart (cardiomegaly): LV dilatation and dysfunction Pericardial effusion

Radiology of the Heart Left atrial enlargement: Straight heart border (LA appendage) Widening of the carinal angle Double contour of the right heart border

Radiology of the Heart LV enlargement: Enlarged cardiac silhouette Prominent left heart border

Radiology of the Heart RV enlargement: Cardiomegaly Straightening of the left heart border Apex displaced upwards Right atrial enlargement: Prominence of the right border of the heart

Radiology of the Heart Lung fields: Congestion & edema in patients with left heart failure Increased blood flow (prominent arteries and veins) in shunt lesions Oligemic lungs in pulmonary stenosis Pleural effusions in advanced heart failure

Two Dimensional Echocardiography Ultrasound beam passing through the heart generates cross sectional images or “slices” of the heart Various structures can be seen in real time

Doppler Echocardiography The derived signal can be plotted graphically against time Or, color can be assigned for the reflected signal and superimposed over the 2D image (color flow mapping)

Two Dimensional Echocardiography indications Assessment of LV function Diagnosis & quantitation of severity of valvular lesions Identification of vegetations Identifying the source of systemic embolism Detection of pericardial effusion

Transoesophageal echocardiography an ultrasound probe in the shape of an endoscope is passed into the oesophagus and positioned immediately behind the left atrium. The high-quality “very clear” images obtained are valuable for investigating patients with: prosthetic (especially mitral) valve dysfunction congenital abnormalities (e.g. atrial septal defect), aortic dissection infective endocarditis to see vegetations that are too small to be detected by ordinary echocardiography systemic embolism.

COMPUTED TOMOGRAPHIC (CT) IMAGING Useful for imaging the chambers of the heart, the great vessels, the pericardium and surrounding structures. In practice it is most useful for imaging the aorta in suspected aortic dissection. Helical CT with multi-slice technology provides images are almost completely devoid of motion artefact

Non-invasive imaging of the coronary arteries (CT coronary angiography) is becoming comparable to conventional coronary arteriography. It is possible to identify coronary artery calcification that gives a correlation with the degree of atherosclerotic disease and quantification of calcified plaques has been used for risk stratification.

non-invasive imaging: CT and MRI Chambers of the heart The great vessels The pericardium Diseases of the aorta The pulmonary arteries Non-invasive imaging of the coronary arteries

Invasive investigation: cardiac catherization A small tube is passed into the heart via a peripheral artery or vein under fluoroscopic guidance Pressure can be measured, flow volumes calculated, radiographic dyes can be injected to outlime the specific chamber or vessel (angiography)

Left heart catheterisation is mainly used to assess coronary artery disease but is also used to evaluate disease of the mitral valve, aortic valve and aorta. Left ventriculography is used to determine the size and function of the left ventricle coronary angiography is used to detect stenoses and guide revascularisation procedures such as balloon angioplasty and stenting.

RADIONUCLIDE IMAGING Blood pool imaging to assess ventricular function Myocardial perfusion imaging

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