ECG Flashcards
At rest, the SA node paces the heart around __ bpm
70
Once the SA node fires, excitation is conducted over both atria. What does this initiate?
atrial contraction
Where and why is there a delay after the atria contracts
slight delay at AV node to full allow the blood in atria to enter ventricles
Describe the electricity of the heart after the AV node.
Once the electricity passes the AV nodes, it moves from the center of the heart downwards. Then it travels back up the heart to innvervate the Purkinje fibers
What does the P-wave interval represent and what is occurring in the heart
Represents: Atrial depolarization (the electrical signal that causes the atria to contract).
What happens in the heart: The sinoatrial (SA) node fires, sending an electrical impulse that spreads across the atria, causing them to contract and push blood into the ventricles.
What does the PR interval represent and what is occurring in the heart
Represents: The time taken for the electrical signal to travel from the atria to the ventricles.
What happens in the heart: The impulse passes through the atrioventricular (AV) node, where it slows down to allow time for the ventricles to fill with blood.
What does the QRS complex represent and what is occurring in the heart
Represents: Ventricular depolarization (the electrical signal that causes the ventricles to contract).
What happens in the heart: The signal moves rapidly through the bundle of His, right and left bundle branches, and Purkinje fibers, causing the ventricles to contract and pump blood into the lungs and body.
What does the ST interval represent and what is occurring in the heart
Represents: The period between ventricular depolarization and repolarization (when the ventricles are contracting but not yet relaxing).
What happens in the heart: Blood is being pumped from the ventricles into the pulmonary artery (right ventricle) and aorta (left ventricle).
What does the T wave represent and what is occurring in the heart
Represents: Ventricular repolarization (the recovery phase, when the ventricles reset electrically for the next heartbeat).
What happens in the heart: The ventricles relax and prepare for the next contraction.
What does the QT interval represent and what is occurring in the heart
Represents: The total time for ventricular depolarization and repolarization.
What happens in the heart: This interval measures how long it takes for the ventricles to contract and fully recover.
What is an accelerometer
a device that measures movments. Most of them move in three directions (up/down, left/right, front/back)
Have them in step-counting watches/phones
Why are 12-leads used in ECG
12-lead ECG provides detailed electrical mapping of the heart by recording signals from 12 different perspectives which helps detect localized abnormalities.
What is an wandering atrial pacemaker (WAP) arrhythmia and how can it be diagnosed?
an atrial arrhythmia that occurs when the cardiac pacemaker site shifts between SA node, atria, and/or AV node.
Seen by changes in P-wave. Might be flattened, notches, or diphasic.
Rarely causes symptoms or requires treatment
What is Multifocal Atrial Tachycardia (MAT) and how can it be diagnosed?
an arrhythmia characterized by an irregularly fast heart rate (≥100 bpm) caused by multiple ectopic foci in the atria
Diagnosed by the presence of three or more distinct P-wave morphologies
What is escape beat/rhythym? How does it happen?
An escape rhythm occurs when the SA node pauses or stops, allowing an ectopic focus (a backup pacemaker) to take over and generate heartbeats. If this happens briefly, it results in an escape beat, while prolonged SA node failure leads to a continuous escape rhythm, seen on ECG as a missed sinus beat followed by a new rhythm.
What is the minimum an ECG must be able to respond to and display (input dynamic range)
as a minimum, ECG must be able to respond to and display a +- 5 mV signal from a direct current voltage in range of -300 to +300 mV
how many samples are collected in one second
200.
what is sampling frequency
samples per second
List some pros and cons of using clinical 12 lead ECG versus data from wearables when training an AI.
Factor Clinical 12-Lead ECG Wearable ECG
Data Quality ✅ High (Multi-lead, less noise) ❌ Lower (Motion artifacts, noise)
Availability ❌ Limited (Medical visits only) ✅ Continuous (24/7 monitoring)
Diversity of Data ❌ Less (Mostly sick patients) ✅ More (Healthy & at-risk populations)
Cost & Accessibility ❌ Expensive & requires professionals ✅ Affordable & widely available
Labeling by Experts ✅ Often labeled by cardiologists ❌ Rarely labeled medically
Diagnostic Power ✅ Can detect ischemia, infarction, arrhythmias ❌ Mostly detects arrhythmias
Regulatory Challenges ✅ Already widely accepted ❌ Needs more validation for approval
Which arrhythmia is characterized by P-wave variability and a heart rate >100 bpm?
Multifocal atrial tachycardia (MAT) Explanation: MAT is defined by ≥3 P-wave morphologies with a fast HR >100 bpm. WAP is similar but slower (<100 bpm).
Which ECG feature distinguishes MAT from atrial fibrillation?
In MAT, distinct P waves are present (though varying in shape). Afib has chaotic baseline with no clear P waves.
During normal cardiac conduction, which pathway conducts the impulse fastest?
Purkinje fibers
What is the input dynamic range a standard ECG must detect?
±5 mV with DC offset up to ±300 mV Explanation: ECG machines must detect very small voltages (±5 mV) and filter out larger DC offsets common in biological signals.
What role does the Bundle of His serve?
Conducts signal from AV node to ventricles
🔹 Explanation: The Bundle of His is the bridge between the AV node and the Purkinje system.
