Ten top tips - 24 hour ECGs
Consultant cardiac electrophysiologists Dr Para Dhillon and Dr Paul Scott with their ten top tips on interpreting 24-hour tapes
1. Holter monitoring may be useful in assessing syncope as well as palpitations
Common indications for Holter monitor testing are the investigation of symptoms of palpitation, dizziness or loss of consciousness with a view to diagnosing tachy- or bradyarrhythmia. The diagnostic yield of Holter monitoring is approximately 11% in the investigation of syncope,1 but up to 70% in the investigation of palpitations.2 Holter monitors are increasingly used to identify asymptomatic atrial fibrillation in patients with stroke. Patients with persistent atrial fibrillation often undergo Holter monitoring to assess ventricular rate control and to guide treatment for the prevention of tachycardia-induced cardiomyopathy.
2. Be aware of normal heart rate variation when making a diagnosis
Holter monitoring may identify considerable normal physiological variation in the heart rate, including sinus tachycardia during exercise approaching 190bpm and nocturnal sinus bradycardia of 30bpm in young adults with high vagal tone. These findings are normal so would not be expected to correlate with symptoms. Always ask the patient to keep a timed symptom diary to correlate with their heart rhythm.
3. Ectopy and minor sinus pauses are not uncommon
In a study of just under 1,300 healthy volunteers with normal baseline 12 lead ECGs,3 atrial or ventricular ectopic beats were found in 60% and 43% of patients, respectively, and 30% had both. Sinus pauses of greater than two seconds were observed in 4% of patients, but pauses or greater than three seconds were rare (0.3%). Supraventricular tachycardia’s were present in 2.2% of those studied and non-sustained ventricular tachycardia in 0.7% of patients.
When interpreting a Holter monitor test, the presence of atrial and ventricular ectopic beats does not necessarily imply a significant cardiac structural or rhythm abnormality. Both forms of ectopy can be treated with beta-blockers or calcium channel blockers if causing symptoms.
4. Short runs of ‘supraventricular tachycardia’ in elderly and hypertensive patients are usually managed medically and cardiology referral is unnecessary
Short runs (5-10 beats) of non-sustained regular atrial tachycardia are commonly seen in elderly and hypertensive patients. These episodes are often described as ‘supraventricular tachycardia’ by the reporting physiologist, but are not due to re-entrant circuits, which are easily amenable to radiofrequency catheter ablation. The P waves are usually visible before the QRS complexes and are sometimes seen in the proceeding T wave.
These short arrhythmias are benign even though they can be rapid (>150bpm). If these atrial arrhythmias cause symptoms they are usually managed with beta-blockers or calcium channel blockers. If these agents are not effective, then it is reasonable to refer to cardiology for consideration of alternative anti-arrhythmic agents.
5. Consider Holter monitoring to ensure adequate rate control in patients with persistent atrial fibrillation
Atrial fibrillation is diagnosed by the presence of irregular RR intervals and no discernible, distinct P waves on the ECG.4 Episodes longer than 30 seconds are considered diagnostic. Episodes of less than 30 seconds are often reported as showing atrial fibrillation but may be due to runs of atrial ectopy instead.
For patients in persistent atrial fibrillation, Holter monitors are used to ensure adequate rate control. Results from the AFFIRM (Atrial Fibrillation Follow-up Investigation of Rhythm Management),5 and RACE (Rate Control Efficacy in Permanent Atrial Fibrillation) II, 6 studies suggest that a mean heart rate of <110bpm is an adequate target for asymptomatic patients.
6. Consider treating asymptomatic patients with a high number of ventricular ectopic beats
Isolated ventricular ectopic beats are observed in 43% of people with normal 12-lead ECGs.3 In a 2016 study, ventricular couplets were observed in four percent of patients but less than 1% had ventricular bigeminy or trigeminy. Only 1% of patients were found to have more than 500 ventricular ectopic beats in a 24-hour period. All types of ventricular ectopy were more common in older individuals (>45 years of age).3
Frequent ventricular ectopic beats may cause a reversible cardiomyopathy in previously fit and well adults. When ventricular ectopic beats account for 10-20% of total QRS complexes on a 24-hour tape, the patient is at risk of developing a left ventricular dysfunction. 7,8 If your patient has ventricular ectopic beats that account for more than 10% of their total QRS complexes on a 24-hour ECG, then they should be offered treatment (beta-blockers, calcium channel blockers, radiofrequency catheter ablation) even if asymptomatic, especially if there is early evidence of left ventricular dysfunction.9
7. Investigate patients with non-sustained ventricular tachycardia to ensure they have a structurally normal heart
Non-sustained ventricular tachycardia (duration of less than 30 seconds) is observed in less than 1% of healthy individuals with normal 12-lead ECGs.3 It is more common in the elderly, those with left ventricular hypertrophy and those with structural heart disease. If the patient has severe left ventricular dysfunction, then the presence of non-sustained ventricular tachycardia is a risk factor for sudden cardiac death and the patient must be referred to a cardiologist for assessment for an implantable cardioverter defibrillator. If the patient has had recent symptoms of syncope then an urgent referral is required, as the syncope may have been caused by sustained haemodynamically unstable ventricular tachycardia. All patients with non-sustained ventricular tachycardia must undergo an echocardiogram to exclude structural heart disease, even if asymptomatic.
8. Young adults and athletic patients may have benign vagally-induced bradyarrhythmias
Holter monitors may identify asymptomatic sinus bradycardia, sinus pauses of less than two seconds, first degree and Mobitz I second degree AV block. There is no prognostic benefit for pacemaker implantation in these patients. Sinus bradycardia, first degree AV block and Mobitz I second degree AV block are particularly common in individuals with high parasympathetic tone, such as young adults and athletes. If present in elderly patients, these findings are more likely to represent early conduction system disease and periodic Holter monitoring is advisable. Those who have symptoms related to bradycardia may be considered for pacemaker implantation.
9. Consider pacemaker implantation in patients with heart block or sinus pauses
The findings of Mobitz II AV block, 2:1 AV block and third-degree AV block are likely to represent significant conduction disease and you should refer these patients urgently for evaluation for pacemaker implantation, even if asymptomic.10 Prophylactic pacemaker implantation in this group is of prognostic benefit.
Symptomatic sinus pauses, or pauses during atrial fibrillation, of greater than three seconds are indications for pacemaker implantation.10 However, asymptomatic nocturnal sinus pauses, or asymptomatic nocturnal pauses during atrial fibrillation, even when greater than three seconds, are not indications for prophylactic pacemaker implantation.
Patients with paroxysmal supraventricular arrhythmias, including atrial fibrillation, may develop long pauses at the termination of their arrhythmia before resumption of sinus rhythm. This effect is due to sinus node inhibition which may be drug or age related. Suppression of the tachyarrhythmia will usually prevent bradycardia. If the tachycardia cannot be effectively managed, then pacemaker implantation may be considered.
10. For patients with infrequent palpitations, prolonged monitoring may be required
A 24-hour ECG may not be suitable when symptoms of palpitation are short-lived and infrequent. In this situation, a self-activated recorder or an event monitor may be indicated. Consider referral to secondary care in this situation.
Dr Para Dhillon and Dr Paul Scott are consultant cardiac electrophysiologists at King’s College Hospital, London.
- Kühne M, Schaer B, Sticherling C, Osswald S. Holter monitoring in syncope: diagnostic yield in octogenarians. J Am Geriatr Soc. 2011;59(7):1293-8.
- Paudel B, Paudel K. The diagnostic significance of the holter monitoring in the evaluation of palpitation. J Clin Diagn Res. 2013;7(3):480-3.
- Hingorani P, Karnad DR, Rohekar P et. al. Arrhythmias Seen in Baseline 24-Hour Holter ECG Recordings in Healthy Normal Volunteers During Phase 1 Clinical Trials. J Clin Pharmacol. 2016;56(7):885-93.
- Kirchhof P, Benussi S, Kotecha D, et al. 2016 ESC Guidelines for the management of atrial fibrillation developed in collaboration with EACTS. Eur Heart J. 2016;37(38):2893-2962.
- Wyse DG, Waldo AL, DiMarco JP, et. al. Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) Investigators. A comparison of rate control and rhythm control in patients with atrial fibrillation. N Engl J Med. 2002;347(23):1825-33.
- Van Gelder IC, Groenveld HF, Crijns HJ et. al. RACE II Investigators. Lenient versus strict rate control in patients with atrial fibrillation. N Engl J Med. 2010;362(15):1363-73.
- Ban JE, Park HC, Park JS et. al. Electrocardiographic and electrophysiological characteristics of premature ventricular complexes associated with left ventricular dysfunction in patients without structural heart disease. Europace. 2013;15(5):735-41.
- Del Carpio Munoz F, Syed FF, Noheria A, Cha YM et. al. Characteristics of premature ventricular complexes as correlates of reduced left ventricular systolic function: study of the burden, duration, coupling interval, morphology and site of origin of PVCs. J Cardiovasc Electrophysiol. 2011;22(7):791-8.
- Pedersen CT, Kay GN, Kalman J et. al. EHRA/HRS/APHRS expert consensus on ventricular arrhythmias. Europace. 2014;16(9):1257-83.
- Brignole M, Auricchio A, Baron-Esquivias G et al. 2013 ESC Guidelines on cardiac pacing and cardiac resynchronization therapy: the Task Force on cardiac pacing and resynchronization therapy of the European Society of Cardiology (ESC). Developed in collaboration with the European Heart Rhythm Association (EHRA). Eur Heart J. 2013;34(29):2281-329