Rcp 276 - Week 3 2007 Xray & Ecg Interpretation

Chest X-Ray and ECG Interpretation More Parts to the Puzzle

X-Rays • First, non-surgical look inside the human body. • Has been refined to include various advanced imaging techniques – CT – MRI – PET scans

X-Rays • Still a simple test that, when done and interpreted properly, can yield a large amount of data.

How X-Rays Work • Simply put: – X-Rays passing through the body penetrate at different rates depending upon the density of the structure they pass through. • High density structures (bone, metal) appear white – This is known as being radio-opaque

• Low density structures appear black (lung tissue, air) – This is known as being radio-lucent

X-Ray Indications • • • •

Detecting pathological changes in the lung Determining the appropriateness of therapy Evaluating the effectiveness of treatment Determining the position of tubes and catheters • Observing the progression of lung disease

X-Ray Views • Different views are taken, they are named for the direction that the X-rays take through the body – PA • Posterior-Anterior

– AP • Anteroposterior

– Lateral – Lateral Decubitus – Etc.

Swan-Ganz and ETT Placement

ETT Placement • 3-5 cm above the carina • Make sure that the ETT is not in the Right main stem Bronchus • Ensure that it is not in the esophagus

Right main stem Intubation

CV Line Placement • Any invasive line placed in the chest has certain inherent risks associated with it – Pneumothorax is one of the predominant ones – Faulty placement of catheters can lead to serious consequences

• Lines need to be placed in the proper location in order for proper function

TPN via a central line into the pleural space

CV Line in the internal jugular

If you start in the Subclavian there are many places you could end up

Chest tubes, Swan Ganz, ETT, and NG tubes all in good position

Chest Tubes • Need to be placed correctly in order to ensure proper function • Why do we place chest tubes?

Tomography • Non-computer aided tomography is not done very much any more • Consisted of a series of films taken via a rotating camera • Resulted in 1 cm cuts • Used to see chest lesions • Replaced by CT and MRI

Standard film showing a density

Tomogram showing the same density

CT Scanning • Frequently utilized, high resolution scan of the chest • Helpful in looking at a lot of different processes – – – – – – – –

Lung tumors Chronic Interstitial Lung Disease AIDS related PNA Occupational Lung Disease Pneumonia Bronchiectasis COPD Chest Trauma

Chest CT of a patient with?

MRI • Role is limited in pulmonary disease • Can evaluate hilar structures better than CT • An enlarged hilum in the presence of known CA is an indication of a poor prognosis where surgery is not an option

X-Ray and MRI of the same patient with Right chest swelling (lymphosarcoma)

VQ Scans • Evaluates the ventilation and perfusion of the lung • Separate studies done and then compared – Ventilation • Patient inhales a radioactive gas (xenon)

– Perfusion • Patient is injected with a radioactive substance that is carried by albumin into the capillaries

VQ Scans • Thought to be highly indicative of Pulmonary Embolus • Recent studies show this to not be true • Another test is better at finding PE – Any ideas?

Normal Perfusion

Ventilation

Is this normal?

Perfusion

Pulmonary Angiography

X-ray Versus CT Versus PET • X-rays may show a defect but not be indicative of what the defect is • CT may show the defect in more detail • In the case of Cancer, PET scans help to locate tumors because of the nature of a tumor’s metabolism – High metabolism picks up the tracer (Fluorine-18 fluorodeoxyglucose) used in PET scan that makes it visible to the camera

X-ray showing density in the right upper lobe

CT showing the density in more detail

PET scan showing the density being localized

X-Rays • It is helpful to understand the location of structures in the chest as they appear on Xray

RML Consolidation

RLL consolidation

Atelectasis • Compressive atelectasis – Results from pneumothorax, hemothorax, and any space-occupying disease of the parenchyma

• Obstructive atelectasis – Results from a bronchial obstruction that cuts off a region of lung from ventilating • Tumor, foreign body, mucous plug

Atelectasis • Classic signs – Shift of fissure lines toward the area of collapse – Movement of the hilar structures toward the area of collapse – Overall loss of volume in one lung – Hemidiaphragm elevation

RUL atelectasis resulting from bronchial obstruction. Inferior border of RUL is pulled upwards towards area of atelectasis

Pneumothorax • Air in the pleural space – Enters through hole in chest or hole in lung

• Tension Pneumothorax – Has a one way valve effect that pumps air into the pleural space and does not let it out – Life threatening • Hilar structures pushed away form effected side, and hemidiaphragm pushed down

Hyperinflation • • • • •

COPD Increased FRC, TLC and RV Large lung volumes Depressed diaphragms Enlarged intercostal spaces

Interstitial Lung Disease • Multiple causes – Occupational, for example?

• X-ray reveals ground glass like appearance – Air bronchograms visualized

CHF • Congestive Heart Failure produces a distinct chest x-ray – Pulmonary vasculature appears more prominent in upper lobes – Heart width increases, exceeds normal ½ of chest width – Kerley’s B Lines appear • Indicative of lymph vessels filling with fluid

Pleural Effusion • Blunting of the costophrenic angle • Small meniscus sign (seen as fluid begin to move up chest wall) • Partially obstructed diaphragm • Complete whiteout in sever cases • Lateral decubitus film helpful in determining if an effusion is present – Change patient’s position and see if fluid shifts.

The ECG • Measures the electrical activity of the heart – Useful for discerning arrhythmias both lifethreatening and non-life-threatening – Useful in identifying an MI as it is occurring

Anatomy of the heart

Heart Cells • Pacemaker cells – Specialized cells that have a high degree of automaticity and provide the electrical power for the heart

• Conducting cells – Cells that conduct the electrical impulse throughout the heart

• Myocardial Cells – Cells that contract in response to electrical stimuli and pump the blood

Electrical Conducting System

Inherent rates for different areas of the heart

Contraction • Depolarization results in the movement of potassium out of the cell and sodium in to the cell causing an electrical shift • Repolarization is the opposite of depolarization when the cell “resets” itself for another cycle • This occurs throughout the heart with every heartbeat

ST segment changes • ST segment is normally isoelectric – Depression of the ST segment and inversion of the T wave indicate myocardial ischemia – Elevation of the ST segment indicates myocardial injury – Significant Q waves indicate infarction has occurred

Lead Placement • Four limb leads and six chest leads yield 12 leads of ECG data – Leads I, II, III, aVR, aVL, aVF, V1, V2, V3, V4, V5, V6

• Different views of the electrical activity of the heart allow us to determine a number of things – Direction of electrical activity in the heart (axis determination) – Location of injury during an MI

Axis Determination • Lead • • • • • •

I and II are Positive I is Positive II is Negative I is negative II is positive I and II are negative

Axis Normal Left axis Right axis Extreme right axis

Axis Determination • Normal Mean Axis is between 0 and 90 degrees. • Right axis deviation indicates that the right ventricle is enlarged • Left axis deviation suggests that the left ventricle is enlarged

Rhythm Interpretation VARIABLE

NORMAL RANGE

INTERPRETATION

Rate

60 – 100 /minute

Rates > 100 = tachycardia Rates <60 = bradycardia

PR Interval

0.12 – 0.20 seconds

> 0.20 = heart block

QRS Interval

<0.12 seconds

> 0.12 = ectopic foci

ST segment

Isoelectric

Elevated = Injury Depressed = Ischemia

T wave

Upright and round

Inverted with ischemia, tall and peaked with electrolyte imbalances

ECG Steps • 1. Identify the Heart Rate – Above 100 = ? – Below 60 = ?

ECG Steps • 2. Evaluate the rhythm – Is it regular, irregular, are there any funny looking beats?

ECG Steps • 3. Note the presence of P waves – One p Wave per QRS, anything else is abnormal • A Fib • A Flutter, etc.

ECG Steps • 4. Measure the PR interval – Longer than normal PR intervals are indicative of heart block

ECG Steps • 5. Measure the QRS interval – Complex is too wide in bundle branch clocks, ectopic beats, etc.

ECG Steps • 6. Inspect the ST segment in all leads – Anterior Wall • V1, V2, V3, V4 • Left anterior descending coronary artery

– Lateral Wall • I, aVL, V5, V6 • LAD, or circumflex

– Inferior Wall • II, III, aVF Right coronary artery

ECG Steps • 7. Identify the mean QRS axis • • • • • •

I and II are Positive I is Positive II is Negative I is negative II is positive I and II are negative

Normal Left axis deviation Right axis deviation Extreme right axis deviation

ECG Steps • 8. Assess the waveform morphology

ECG Steps • 9. Evaluate the Q wave – Could indicate the presence of an old MI

ECG Steps • 10. Look for signs of chamber enlargement – High voltage waves indicate hypertrophy

ECG Steps Simplified • 1. Determine the regularity (rhythm) – Is it regular or irregular

• 2. Calculate the rate • 3. Examine the P waves – One for every QRS?

• 4. Measure the PR interval • 5. Measure the QRS complex