Investigations of CVS

Investigations of the Cardiovascular system

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At the end of this lecture, you should be able to appreciate

The usefulness of each investigation in diagnosing cardiac disease
Each type of investigation clarifies and detects a certain aspect of cardiac pathology
Non-invasive investigations are increasingly replacing the old, invasive techniques.
Rapidly evolving methods of investigation because of the advances achieved in technology

Investigations of the CVS

BNP, Troponin
Electrocardiography
Radiology
Echocardiography
CT imaging
MRI
Cardiac catheterization
Radionuclide imaging
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BNP, Pro-BNP
Peptide released from the atria in response to stretch
Very sensitive for the diagnosis of congestive heart failure
Levels fall with improvement of heart failure on treatment, rise with worsening
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Troponin

Protein contained within cardiac muscle
Released when cardiac muscle is injured e.g. ischemia or inflammation
Very useful in the diagnosis and follow up of patients with acute coronary syndrome
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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.)
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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
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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
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Imaging

The principle of imaging is to reconstruct a three-dimensional structure out of a group of two dimensional images:
Silhouette imaging: various structures are overlapped over each other e.g. CXR, angiography, nuclear imaging
Tomographic imaging: a group of sections through the structure to be examined e.g. echo, CT, MRI

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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
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Radiology of the Heart

Cardiac size:
Cardio-thoracic ratio (CTR):
Normally < 0.5
Enlargement of the heart (cardiomegaly):


LV dilatation and dysfunction
Pericardial effusion




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Radiology of the Heart

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





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Radiology of the Heart

LV enlargement:
Enlarged cardiac silhouette
Prominent left heart border




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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

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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
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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



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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
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Doppler Echocardiography

Sound waves reflected from moving RBCs undergo frequency shift
The faster the blood velocity , the greater the frequency shift
The direction of moving blood determines whether the reflected signal is positive or negative

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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)
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3-Dimentional Echocardiography

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Other 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



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Invasive investigation: cardiac catherization

A small tube (catheter) 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 infected to outline the specific chamber or vessel (angiography)
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