Skip to content
How It Works
Explore
Ask a Question Resources Pricing
Who It's For
Patients
Decode results, prep for appointments, weigh options.
Caregivers & advocates
Carry the research load for someone you love.
Providers & clinicians
Resources for patients in your practice.
Log In Sign Up
PubMed This is a summary of 17 peer-reviewed journal articles Updated
Cardiology

Diagnostic Testing: ECGs, Holter Monitors, and Echocardiograms

At a Glance

Atrial conduction disease is evaluated with an ECG for P-wave changes, longer-term monitors for intermittent rhythm problems, and an echocardiogram for atrial size and heart function. Matching results with symptoms helps guide follow-up.

Diagnosing atrial conduction disease involves combining different types of medical tests. Because electrical “glitches” can be fleeting, your medical team uses a combination of “snapshots” (ECGs), “movies” (ambulatory monitors), and “architectural blueprints” (Echocardiograms) to understand what is happening inside your heart [1][2].

The 12-Lead ECG: The Diagnostic Snapshot

A standard 12-lead Electrocardiogram (ECG) is the primary tool used to identify conduction issues. It records the electrical activity of your heart from 12 different angles. For atrial conduction disease, doctors look specifically at the P-wave, which represents the signal activating your atria [3].

  • P-wave duration ≥120ms: In plain English, this means the electrical signal is taking 120 milliseconds or longer to travel across the top of your heart [4]. A normal P-wave is typically shorter. If your P-wave is wider than 120ms, it is the defining feature of Interatrial Block (IAB) [3].
  • Partial vs. Advanced IAB:
    • Partial IAB: The P-wave is simply wide (≥120ms), showing the signal is moving slowly [3].
    • Advanced IAB: The P-wave is wide AND has a “biphasic” (up-and-down) shape in the bottom leads of the ECG (leads II, III, and aVF) [5]. This indicates a marked conduction delay where the electrical signal activates the left atrium through an altered or retrograde route [5].

Ambulatory Monitoring: The Heart “Movie”

Because your heart might behave perfectly while you are in the doctor’s office, “ambulatory” (mobile) monitors are used to record your heart over a longer period.

  • Holter Monitors: These are typically worn for 24 to 48 hours. They are excellent for catching daily symptoms or frequent arrhythmias [6].
  • Patch Monitors: These are small, lead-free stickers worn for up to 14 days. Longer monitoring generally increases the chance of capturing intermittent events, like hidden AFib or occasional bradycardia, though the diagnostic yield varies based on your specific situation [6].
  • Implantable Loop Recorders (ILR): For symptoms that happen very infrequently, a tiny device can be placed under the skin. It can monitor your heart for up to 3 years. An ILR is not a routine test for isolated IAB; it is usually reserved for selected unexplained syncope (fainting) or cryptogenic stroke [7][8].

Echocardiograms: Checking the Structure

An echocardiogram (or “echo”) is an ultrasound of the heart. While it doesn’t measure electricity, it evaluates the physical structure and pumping function of the heart [9].

Doctors use the echo to look for left atrial enlargement. While left atrial enlargement is a marker of pressure loading or shared atrial remodeling, it is not proof of fibrosis or a direct cause of IAB [10][11]. Enlargement can have multiple causes, including hypertension or valve disease. Knowing the size and function of your atria helps your doctor assess your overall risk [12][13].

Your ECG Completeness Checklist

When you review your ECG and monitor results with your care team, ensure you discuss these specific points:

  1. P-wave Duration: Is my P-wave duration at least 120ms? [3]
  2. Morphology: Is the P-wave “biphasic” (plus-minus shape) in the bottom leads, suggesting advanced IAB? [5]
  3. Heart Rate Trends: What was my lowest (bradycardia) and highest (tachycardia) heart rate during the recording, and does it align with my activity? [14]
  4. Pauses: Were there any “pauses” in my heart rhythm? If so, how many seconds did they last, and what was I doing at the time? [15][16]
  5. Symptom Matching: Did any electrical findings happen at the exact same time I logged feeling dizzy or tired? [17]

Common questions in this guide

What does a P-wave of 120 milliseconds or longer mean?
The P-wave shows the electrical signal moving through the atria, the heart’s upper chambers. A duration of 120 milliseconds or longer is a widened P-wave and is the defining ECG feature of interatrial block. Your clinician must interpret it with the rest of the ECG and your clinical picture.
How are partial and advanced interatrial block different?
Partial interatrial block means the P-wave is widened, showing slower signal travel. Advanced block has a widened P-wave plus an up-and-down, or biphasic, shape in ECG leads II, III, and aVF, indicating a more marked delay and an altered route to the left atrium.
Which heart monitor is best when symptoms do not happen every day?
A 24- to 48-hour Holter monitor is useful when symptoms or rhythm changes happen daily or often. A patch monitor can record for up to 14 days and may be more useful for less frequent events, while an implantable loop recorder is reserved for selected people with very infrequent unexplained fainting or a stroke with no identified cause. Your clinician chooses based on how often symptoms occur.
What can an echocardiogram tell me about atrial conduction disease?
An echocardiogram uses ultrasound to assess heart structure, chamber size, and pumping function. It can show whether the left atrium is enlarged, but enlargement alone does not prove scarring or directly cause interatrial block. High blood pressure and valve disease are among the possible causes of an enlarged left atrium.
How can my doctor tell whether dizziness or palpitations are related to my heart rhythm?
A monitor is most helpful when a recorded rhythm change occurs at the same time as a symptom you logged. Write down when you feel dizzy, tired, or have palpitations, along with what you were doing, and ask about heart-rate highs, lows, and pauses. This symptom-and-recording match helps your care team interpret the results.
What does tachy-brady syndrome mean on a heart monitor?
Tachy-brady syndrome refers to alternating episodes of fast and slow heart rates. A monitor may help identify these patterns and when they occur, but your clinician must interpret them alongside your symptoms and other test findings.

Get notified when new evidence is published on Atrial conduction disease.

We monitor PubMed for new peer-reviewed studies on this topic and email a short summary when something meaningful changes.

References

References (17)
  1. 1

    [Bradyarrhythmias: diagnostics].

    Israel CW

    Deutsche medizinische Wochenschrift (1946) 2016; (141(10)):718-28 doi:10.1055/s-0042-103296.

    PMID: 27176067
  2. 2

    Multimodal Cardiac Imaging in the Assessment of Patients Who Have Suffered a Cardioembolic Stroke: A Review.

    Thong EHE, Kong WKF, Poh KK, et al.

    Journal of cardiovascular development and disease 2023; (11(1)) doi:10.3390/jcdd11010013.

    PMID: 38248883
  3. 3

    Intra- and interatrial conduction abnormalities: hemodynamic and arrhythmic significance.

    Johner N, Namdar M, Shah DC

    Journal of interventional cardiac electrophysiology : an international journal of arrhythmias and pacing 2018; (52(3)):293-302 doi:10.1007/s10840-018-0413-4.

    PMID: 30128800
  4. 4

    Interatrial Block, Bayés Syndrome, Left Atrial Enlargement, and Atrial Failure.

    Bejarano-Arosemena R, Martínez-Sellés M

    Journal of clinical medicine 2023; (12(23)) doi:10.3390/jcm12237331.

    PMID: 38068382
  5. 5

    A rare combination of atrial and intraventricular conduction disturbances: Atypical type I advanced interatrial block, left posterior fascicular block and transient right bundle branch block.

    Manzzardo J, Barbosa-Barros R, Nikus K, Pérez-Riera AR

    Journal of electrocardiology 2021; (65()):45-49 doi:10.1016/j.jelectrocard.2020.12.004.

    PMID: 33497882
  6. 6

    A Patch-Type Electrocardiography Is Superior to Holter Monitoring for Detecting Paroxysmal Cardiac Arrhythmias.

    Kim YG, Choi JI, Oh IY, et al.

    Journal of Korean medical science 2025; (40(28)):e168 doi:10.3346/jkms.2025.40.e168.

    PMID: 40696526
  7. 7

    Usefulness of an Implantable Loop Recorder in Diagnosing Unexplained Syncope and Predictors for Pacemaker Implantation.

    Lee SH, Kim TH, Oh YS, et al.

    Journal of Korean medical science 2020; (35()):e11 doi:10.3346/jkms.2020.35.e11.

    PMID: 31920017
  8. 8

    Detection rate by time period and predictors of serious arrhythmias in unexplained syncope: a multicenter implantable loop recorder registry study.

    Kim J, Oh IY, Cha MJ, et al.

    The Korean journal of internal medicine 2025; (40(4)):616-625 doi:10.3904/kjim.2024.364.

    PMID: 40635488
  9. 9

    Atrial fibrillation with slow-ventricular response (AF-SVR): A literature review.

    Choi J, Kong D, Katic L, et al.

    The journal of medicine access 2025; (9()):27550834251342890 doi:10.1177/27550834251342890.

    PMID: 40607080
  10. 10

    Electrophysiological Mechanisms of Bayés Syndrome: Insights from Clinical and Mouse Studies.

    Tse G, Lai ET, Yeo JM, Yan BP

    Frontiers in physiology 2016; (7()):188 doi:10.3389/fphys.2016.00188.

    PMID: 27303306
  11. 11

    Left Atrial Enlargement on Transthoracic Echocardiography Predicts Left Atrial Thrombus on Transesophageal Echocardiography in Ischemic Stroke Patients.

    Anaissie J, Monlezun D, Seelochan A, et al.

    BioMed research international 2016; (2016()):7194676 doi:10.1155/2016/7194676.

    PMID: 27822477
  12. 12

    Prevalence of clinically significant bradyarrhythmias in patients implanted with loop recorders for cryptogenic stroke: A manifestation of atrial cardiomyopathy?

    Bencardino G, Festa PA, Scacciavillani R, et al.

    Heart rhythm 2026; (23(4)):e653-e658 doi:10.1016/j.hrthm.2026.01.011.

    PMID: 41519354
  13. 13

    Severe functional tricuspid regurgitation due to wild-type transthyretin amyloid cardiomyopathy without left ventricular hypertrophy: a case report.

    Matsuzoe H, Tanaka H, Sato S, Otani K

    European heart journal. Case reports 2022; (6(12)):ytac462 doi:10.1093/ehjcr/ytac462.

    PMID: 36530462
  14. 14

    Sick Sinus Syndrome.

    De Ponti R, Marazzato J, Bagliani G, et al.

    Cardiac electrophysiology clinics 2018; (10(2)):183-195 doi:10.1016/j.ccep.2018.02.002.

    PMID: 29784479
  15. 15

    Incidental Arrhythmias During Atrial Fibrillation Screening With Repeat 7-Day Holter ECGs in a Hospital-Based Patient Population.

    Goulouti E, Lam A, Nozica N, et al.

    Journal of the American Heart Association 2024; (13(4)):e032223 doi:10.1161/JAHA.123.032223.

    PMID: 38348803
  16. 16

    Real-world use of theophylline in critically ill patients with sinus pauses: a case series.

    Elahi MA, Jalal H, Frick W, Kraft BD

    Frontiers in cardiovascular medicine 2026; (13()):1731993 doi:10.3389/fcvm.2026.1731993.

    PMID: 41778069
  17. 17

    [Sinus bradycardia and syncope: what pathophysiological mechanism and what management of the patient?]

    Alboni P, Stucci N, Parisi C

    Giornale italiano di cardiologia (2006) 2017; (18(11)):774-780 doi:10.1714/2803.28363.

    PMID: 29105672

This page explains how ECGs, heart monitors, and echocardiograms are used to evaluate atrial conduction disease for informational purposes only and does not constitute medical advice. Your cardiology team should interpret your results in the context of your symptoms and medical history.

Guide contents Atrial conduction disease
Research & Literature
02 Symptoms and Warning Signs 04 Surveillance and Lifestyle Management