ECG in Pulmonary Medicine

Role of ECG in the diagnosis of Pulmonary Diseases


Introduction
Electrocardiography is a useful adjunct to other pulmonary tests because it provides information about the right side of the heart and therefore pulmonary disorders such as chronic pulmonary hypertension and pulmonary embolism. Since the electrical activity of the heart is influenced to an extent by the surrounding lungs, proper evaluation of ECG can throw light to many lung diseases. When the lung hyperinflates the heart become tubular-vertical heart- and the ECG shows corresponding changes. Similarly most of the chronic lung diseases leads on to right ventricular hypertrophy and hence ECG findings reflects that of clockwise rotation of the heart.
For better understanding of the ECG changes in pulmonary diseases, the physician should be aware of the P wave axis, QRS axis, rotation of the heart in vertical and horizontal axis and various arrhythmias.
Basics in ECG

1) Electrical axis of the Heart








• Both I and aVF +ve = normal axis
• Both I and aVF -ve = axis in the Northwest Territory
• Lead I -ve and aVF +ve = right axis deviation
• Lead I +ve and aVF -ve
o lead II +ve = normal axis
o lead II -ve = left axis deviation

Causes of a Northwest axis
• Emphysema
• Hyperkalaemia
• Lead transposition
• Artificial cardiac pacing
• Ventricular tachycardia
Causes of right axis deviation
• Normal finding in children and tall thin adults
• Right ventricular hypertrophy
• Chronic lung disease even without pulmonary hypertension
• Anterolateral myocardial infarction
• Left posterior hemiblock
• Pulmonary embolus
• Wolff-Parkinson-White syndrome - left sided accessory pathway
• Atrial septal defect
• Ventricular septal defect
Horizontal heart
Description of the heart's electrical position; recognized in the electrocardiogram when the QRS in lead aVL resembles that in V6 and QRS in aVF resembles that in V1; also, loosely, when the electrical axis lies between −30° and +30°.
Vertical heart
Loosely descriptive of the heart's electrical axis when it is directed at approximately +90, recognized in the electrocardiogram when the QRS complex in lead aVL resembles V1 while that in aVF resembles V6.
Clockwise and Counterclockwise rotation
Clockwise and counterclockwise rotation refers to a change in the electrical activity in a horizontal plane through the heart. If the electrical activity of the heart has turned more to the right side of the patient this is called counterclockwise rotation. If the electrical activity of the heart has turned more to the left side of the patient this is called clockwise rotation.
Clockwise and counterclockwise rotation can be assessed only in the chest-leads (V1 - V6). Normally the R wave amplitude increases from V1 to V5. Around V3 or V4 the R waves become larger than the S waves and this is called the 'transitional zone'. If the transition occurs at or before V2, this is called counterclockwise rotation. If the transition occurs after V4, this is called clockwise rotation.
Causes of clockwise rotation:
• Intraventricular conduction abnormalities secondary to myocardial degeneration
• Right ventricular heart disease
• Shift of the septum to the left
• Dilated cardiomyopathy
• Shift of the whole heart
• Pulmonary emphysema
• Vertical heart (usually thin and tall persons)
Causes of counterclockwise rotation:
• Electrical shift to the right
• Left ventricular hypertrophy
• WPW Syndrome
• Posterior myocardial infarction
• Left septal fascicular block
• Shift of the septum to the right
• Hypertrophic cardiomyopathy
P-Wave Abnormalities
Right atrial enlargement:
• P-wave axis ≥ +750 (low specificity)
• P-wave > 0.15 mV in V1 or V2 (best criterion)
P Pulmonale
• Peaked P-waves ≥ 0.25 mV in II, III, or aVF
• P-wave axis ≥ +750
• Degree of rightward P-wave axis correlates better with lung disease severity than P-wave amplitude
• P-wave amplitude correlates better with RA strain (may be transient)
Right Ventricular Hypertrophy
• RAD ≥ +110 0
• R/S ratio in V1 or V3R > 1
• qR in V1 or V3R (usually seen in severe RVH)
• rSR’ in V1 with R’ > 0.7 mV
• R/S ratio in V5 or V6 ≤ 1
• R-wave in V1 > 0.7 mV
• S-wave in V2 < 0.2 mV • Onset of intrinsicoid deflection in V1 > 35 ms
Need at least two criteria for definite diagnosis.
• Type A – severe RVH as seen in severe PAH, end- stage COPD, severe VPS
• Type B – mild to moderate RVH (must differentiate from true posterior MI)
• Type C – moderate RVH as seen in Mitral Stenosis, or moderate COPD and occasionally in ASD
• IRBBB – moderate RVH or RVOT hypertrophy as seen in ASD, moderate COPD
All types of RVH are usually associated with some degree of RAD
• Intermittent hypoxia and pulmonary vasoconstriction
• Right atrial “strain”
• Right atrial enlargement
• “Clockwise” rotation of the heart
• RVH (usually mild or mod. unless end-stage)
• Lung hyperinflation
• Depressed diaphragms
• Rightward QRS axis
• P Pulmonale (peaked & >0.25 mV) in II, III, aVF
• Shift of transition leftward
• Low voltage in limb leads
• Type B or C RVH (late)
• Transient atrial arrhythmias
Arrhythmias
Changes in the myocardium due to hypoxia and chamber hypertrophy leads on to many rhythm disturbances. Most of them are tachyarrhythmias especially atrial tachycardia. They include atrial flutter, fibrillation, multifocal atrial tachycardia and rarely ventricular arrhythmias.






ECG Criteria for COPD

COPD due to its hyperinflation retards the transmission of electrical activity to the chest wall. Moreover persistent hypoxia, resultant pulmonary hypertension and cor pulmonale influences the myocardial activity.Hence many ECG changes are observed in COPD.Most of them are non specific and cannot contribute to diagnosis. But proper evaluation ECG is needed in all patients to detect early complications and appropriate interventions.
The most frequently observed findings are
• P pulmonale (peaked P ≥ 0.25 mV in II, III, aVF)
• P wave axis ≥ +800
• QRS amplitude ≤ 0.5 mV in all limb leads
• QRS axis > +900
• QRS amplitude ≤ 0.5 mV in V5 , V6
• S1S2S3 pattern with R/S < 1 in I, II, III • L1 sign of emphysema (Deep S wave in Lead 1) • Atrial arrhythmias (especially MAT) COPD likely to be present if one P and one QRS criterion present Other ECG findings in COPD • P-wave axis > +700 = 89% sensitive and 96% specific
• Degree of QRS RAD correlated with severity, but QRS axis > +900 in only 8%
• P axis > + 600 in 60% of cases
• S1S2S3 pattern in only 25 % of case
• Leftward QRS transition with R/S < 1 in V5 V6 (type C RVH) = severe (end-stage) COPD
• In severe cases of Cor pulmonale, there will be changes of left ventricular involvement such as ST-T changes in left precordial leads, LBBB and ventricular tachyarrhythmias.

ECG in Pulmonary Hypertension

The electrocardiogram (ECG) may demonstrate signs of right ventricular hypertrophy or strain, including right axis deviation, an R wave/S wave ratio greater than one in lead V1, incomplete or complete right bundle branch block, or increased P wave amplitude in lead II (P pulmonale) due to right atrial enlargement. Most ECG signs are specific but not sensitive for the detection of right ventricular disease. ECG changes cannot determine disease severity or prognosis



ECG in Cor Pulmonale

Electrocardiographic (ECG) abnormalities in cor pulmonale reflect the presence of right ventricular hypertrophy (RVH), RV strain, or underlying pulmonary disease. Such ECG changes may include the following:
• Right axis deviation
• R/S amplitude ratio in V1 greater than 1 (an increase in anteriorly directed forces may be a sign of posterior infarction)
• R/S amplitude ratio in V6 less than 1
• P-pulmonale pattern (an increase in P wave amplitude in leads 2, 3, and aVF)
• S1 Q3 T3 pattern and incomplete (or complete) right bundle branch block, especially if pulmonary embolism is the underlying etiology
• Low-voltage QRS because of underlying COPD with hyperinflation

Severe RVH may reflect as Q waves in the precordial leads that may be mistakenly interpreted as an anterior myocardial infarction. Additionally, many rhythm disturbances may be present in chronic cor pulmonale; these range from isolated premature atrial depolarizations to various supraventricular tachycardias, including paroxysmal atrial tachycardia, multifocal atrial tachycardia, atrial fibrillation, atrial flutter, and junctional tachycardia. These dysrhythmias may be triggered by processes secondary to the underlying disease, (eg, anxiety, hypoxemia, acid-base imbalance, electrolyte disturbances, excessive use of bronchodilators, heightened sympathetic activity). Life-threatening ventricular tachyarrhythmias are less common.

ECG in Pulmonary Thromboembolism

ECG findings are mostly nonspecific in pulmonary embolism. Most frequent abnormality is tachycardia followed by ST-T changes. The frequently referred S1Q3T3 sign is seen only in 11-50% of cases.
• Sinus tachycardia: 8-73%
• Sympathetic stimulation
• Acute pulmonary hypertension
• RA & RV strain/dilatation
• Spatial changes (clockwise rotation)
• ↑ RV wall stress leading to RV ischemia
• RV dysfunction
• Sinus tachycardia
• P pulmonale
• RBBB (complete or incomplete)
• Acute rightward axis shift
• S1Q3T3 pattern (? IMI)
• ↓ T V1-V3 (frequently persistent) (? ASMI)
• Atrial arrhythmias (Atrial Fibrillation or Atrial Flutter)
• P Pulmonale: 6-33%
• Rightward axis shift: 3-66%
• Inverted T-waves in ≥ 2 Rt chest leads: 50%
• S1Q3T3 pattern: 11-50%
• S1 – 60%, Q3 – 53%, ↓T3 – 20%
• Clockwise rotation: 10-56%
• RBBB (complete or incomplete): 6-67%
• AF or AFlutter: 0-35%
• No ECG changes: 20-24%





ECG in Dextrocardia
• Global negativity in lead I (a negative P-wave, QRS complex and T-wave)
• Positively deflected QRS complex in aVR
• Negative P-wave in lead II
• Reverse R-wave progression in precordial leads
• Right axis deviation.


The finding of a positively deflected QRS complex in aVR and a negative in lead I should cause concern for the treating paramedic. The most common cause for this finding is reversed electrode placement. If this situation presents and the clinician has assured correct limb lead placement, dextrocardia should be on the list of differentials. Once again, consider ventricular arrhythmias first.
R-wave progression is defined as the transition of a predominantly negative QRS complex in V1 to a predominantly positive QRS complex in V6 on the 12-lead ECG.
The change that is a normal variant with dextrocardia is a reversal of this normal pattern, which would present as a predominant R-wave in V1 and a predominant S-wave in V6.

ECG in Hypoxia
• Shortening of R-R interval
• Increase of P wave
• Prolongation of P-Q
• Deviation of the R vector
• T wave flattening in the left precordial leads

ECG in Pericardial Effusion
• The QRS axis alternates between beats( Electrical alternance)
• ST-segment elevation
• PR-segment depression
• Low voltage complex

ECG in Pneumothorax

• Depend on the size of the pneumothorax
• Caused by displacement of the heart
• Most often RAD, independent of the pneumothorax site
• Low voltage frequently present
• QS complexes in precordial leads also common
• T-wave inversions simulate ischemia
• Occasionally ST elevations mimic injury

ECG in ASD

• Secundum: RAD and IRBBB type RVH (RV volume overload) in ≈ 60%
• Primum: LAFB (almost 100%) ± IRBBB (depending on shunt magnitude)
• Sinus Venosus: Ectopic atrial rhythm
(Inverted P waves II, III, AVF in ≈30%)

ECG in VSD

• LVH or BVH depending on site of the VSD
and magnitude of the L-R shunt
• RVH (usually severe type A) with pulmonary vascular disease (Eisenmenger syndrome)

Conclusion
ECG is an important diagnostic tool in many pulmonary diseases. It can supplement other investigations and in the hands of an expert physician ECG it is a cheap and easily available tool to pinpoint many respiratory diseases.