CH 18.4 Rhythms Originating in The Atria

What is the primary use of a 12-lead ECG?

To localize cardiac muscle injury sites and identify cardiac abnormalities.

What are some indications for performing a 12-lead ECG?

Chest pain, electrical injury, electrolyte imbalance, medication overdose, RVF/LVF, post-syncope, stroke, syncope or near-syncope, hemodynamic instability.

What mode is used for rhythm interpretation in a 12-lead ECG?

Monitor mode.

What is the frequency range captured in monitor mode of a 12-lead ECG?

1 to 150 Hz.

What is the purpose of diagnostic mode in a 12-lead ECG?

It filters out very little electrical information and records a 12-lead ECG by default.

What is the seven-step method for interpreting a 12-lead ECG?

Review the snapshot, interpret the dysrhythmia, determine the axis, identify conduction system disturbances, evaluate chamber size, review for zones of ischemia, injury, and infarction, and identify noncardiac causes.

What should you check during the snapshot review of a 12-lead ECG?

Ensure all leads printed, check for artifacts, and assess if the rate is at extremes.

What are the components of dysrhythmia interpretation in a 12-lead ECG?

Identify waves (P-QRS-T), measure PRI, measure QRS duration, determine rhythm regularity, and measure heart rate.

What does the QRS axis represent?

The average of all vectors created by the ventricles during depolarization.

How is the QRS wave viewed from lead I determined?

Positive if heading toward the left arm, negative if heading toward the right arm.

How is the QRS wave viewed from lead aVF determined?

Positive if heading toward the feet, negative if heading toward the head.

What does the QRS axis indicate about ventricular health?

It moves toward hypertrophy and away from infarction.

What characterizes a right bundle branch block (RBBB)?

QRS complex with a bizarre appearance and longer than 0.12 seconds, with a terminal R wave in lead V1.

What characterizes a left bundle branch block (LBBB)?

Terminal S wave in lead V1 and terminal R waves in leads I, aVL, and V6.

What indicates an anterior fascicular block?

rS complexes in leads II, III, aVF and qR complexes in leads I and aVL.

What indicates a posterior fascicular block?

qR complexes in leads II, III, aVF and rS complexes in lead I.

What is a bifascicular block?

Two or more blocked fascicles or conduction pathways.

What is a trifascicular block?

All three components are blocked or impaired.

What are signs of right atrial abnormality on a 12-lead ECG?

P wave amplitude higher than 2.5 mm in lead II and/or higher than 1.5 mm in lead V1.

What characterizes left atrial abnormality?

P wave longer than 0.12 seconds in lead II, notched appearance, and biphasic P wave in lead V1.

What is the significance of measuring chamber size in a 12-lead ECG?

It helps identify right atrial abnormality, left atrial abnormality, right ventricular hypertrophy (RVH), and left ventricular hypertrophy (LVH).

What is the importance of lead placement during a 12-lead ECG?

Proper lead placement ensures accurate readings and prevents patient discomfort.

What should be done to ensure patient comfort during a 12-lead ECG?

Make sure the patient does not get chilled.

What is the frequency range for electrical information in diagnostic mode?

0.05 to 150 Hz.

What is the default recording for a 12-lead ECG?

It records a 12-lead ECG by default.

What are common causes of predominantly negative ECG findings?

Valvular heart disease, hypertensive heart disease, cardiomyopathy, and coronary artery disease (CAD).

What condition is usually indicated by right ventricular hypertrophy?

Pulmonary hypertension.

How is right ventricular hypertrophy diagnosed?

By an R wave that exceeds the height of the S wave in lead V1.

What causes left ventricular hypertrophy?

Hypertension or cardiac abnormalities.

What are the diagnostic criteria for left ventricular hypertrophy?

Deepest S wave in V1 plus tallest R wave in V5/V6 taller than 35 mm, and/or R wave in lead aVL taller than 11 mm.

What is the significance of ST-segment depression on an ECG?

It indicates ischemia.

What does ST-segment elevation signify on an ECG?

Myocardial injury.

What are pathologic Q waves indicative of?

Infarction.

What does ST-segment depression greater than 0.5 mm in two or more contiguous leads suggest?

Unstable angina or NSTEMI.

What ST-segment elevation criteria indicate STEMI in men older than 40?

ST-segment elevation of 2 mm or more in leads V2 and V3.

What ST-segment elevation criteria indicate STEMI in women?

ST-segment elevation of 1.5 mm or more in leads V2 and V3.

What factors are considered for treatment decisions in suspected myocardial infarction?

Patient presentation and history, 12-lead ECG findings, and laboratory test results.

What are reciprocal changes in ECG interpretation?

Mirror image changes that help identify myocardial infarction.

What is benign early repolarization characterized by?

ST-segment elevation, J or fishhook appearance at the J point, and concave ST-segment morphology.

What symptoms are associated with pericarditis?

Positional chest pain, shortness of breath, and a history of recent infection or fever.

What does diffuse ST-segment elevation and depressed PR segment indicate?

Pericarditis.

What ECG findings are associated with pulmonary embolism?

An S1Q3T3 pattern, new right bundle branch block (RBBB), and ST-segment depression in leads V1 to V3.

What are the ECG characteristics of hypothermia?

May develop J waves, reveals a bradycardic rhythm, and may show ST-segment depression and T-wave inversion.

What are the ECG findings in hyperkalemia?

Tall, peaked, asymmetric T waves with flattened P waves and wide QRS complexes in severe cases.

What are the ECG findings in hypokalemia?

Flat or seemingly absent T and U waves.

What does hypercalcemia indicate on an ECG?

Shortened QT interval.

What does hypocalcemia indicate on an ECG?

Lengthened QT interval.

What is dilated cardiomyopathy characterized by?

Weakening of the heart muscle and its ability to pump blood, leading to enlargement and stretching of the heart.

What characterizes hypertrophic cardiomyopathy?

Thickening of myocardial walls, often genetic, leading to symptoms like shortness of breath, chest pain, and syncope.

What is restrictive cardiomyopathy?

A condition where ventricular walls stiffen due to abnormal substances.

What is Brugada syndrome?

A disorder involving sodium channels in the heart, characterized by incomplete RBBB and ST-segment elevation that returns to baseline.

What defines long QT syndrome (LQTS)?

QT interval exceeding 0.44 seconds, resulting from genetic mutations, certain drugs, or conditions like hypocalcemia.

What ECG findings are associated with intracranial hemorrhage?

Inverted, symmetric T waves in precordial leads and prolonged QT intervals.