1. Investigations of the Cardiovascular system

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

3. 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.)

4. Principles of the ECG
depolarization starts in the sino-atrial node (SA node), spreads through the two atria (sinus rhythm)

5. Principles of the ECG
Transmitted to the ventricles via the AV node, which conducts slowly and regulates the frequency of conduction to the ventricles

6. Principles of the ECG
Normally, the AV node is the only route of impulse transmission to the ventricles. In other areas, the atria are insulated from the vnetricles by the annulus fibrosus

7. Principles of the ECG
The bundle of His passes from the AV node through the annulus fibrosus and divides into the right bundle (RBB) and left bundle (LBB) branches

8. Principles of the ECG
Each bundle branch passes along the corresponding septal surface of the heart & radiates out as the Purkinje system
The left bundle divides into the anterior & posterior fascicles

9. Principles of the ECG
Activation of the SA node is not detected on the surface ECG

10. Principles of the ECG
Impulse transmission down the atria triggers atrial contraction & is recorded as the P wave

11. Principles of the ECG
The PR interval represents the delay between the onset of atrial depolarization and the beginning of ventricular depolarization

12. Principles of the ECG
The depolarization wave then spreads to the two ventricles causing ventricular contraction and producing the QRS complex

13. Principles of the ECG
The muscle mass of the ventricles is larger than that of the atria, so the QRS amplitude is greater than that of the P wave.

14. Principles of the ECG
Repolarization starts ~ 300 msec after the end of depolarization
The interval from the end of the S wave to the beginning of the repolarization (T) wave is the ST segment, which is normally iso-electric

15. Principles of the ECG
Repolarization of the myocardium produces the T wave
The QT interval represents the total duration of ventricular depolarization & repolarization

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

17. 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

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

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

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

21. 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

22. 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

23. 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 if sections through the structure to be examined e.g. echo, CT, MRI

24. 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

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

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

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

28. 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

29. 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

30. 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

32. 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

37. 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

40. 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)

42. 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

43. 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 infected to outlime the specific chamber or vessel (angiography)