It is rather uncommon for healthy, young persons to have significant rhythm disturbances; in fact, several arrhythmias are not necessarily abnormal, including sinus bradycardias (35^10 beats/ minute), sinus arrhythmias (with pauses up to 3 seconds), sinoatrial exit block, Wenckenbach block (second-degree AV block type I), wandering atrial pacemaker, junctional escape complexes, and premature atrial or ventricular contractions.
Of concern are frequent and complex atrial and ventricular rhythm disturbances that are less commonly observed in normal subjects, including second-degree AV block type II, sinus pauses 3 seconds, and brady- or tachyarrhythmias associated with symptoms. Results of the Holter monitor need to be analyzed with the diary to correlate specific symptoms to the rhythm and rate recorded.
What is the role of the Holter monitor in patients with known ischemic heart disease?
Patients post MI and those with other forms of ischemic heart disease frequently have premature ventricular contractions (PVCs). After MI the frequency of PVCs increases for several weeks and then declines after 6 months. The frequency and complexity of PVCs are independent markers for sudden death or acute cardiac event; risk may be increased 2-5 times. Patients with symptoms and known ischemic heart disease are in a higher risk group and should be evaluated with both a Holter monitor and SAECG.
Can Holter monitors assist in the diagnosis of suspected ischemic heart disease?
Yes. Transient ST-segment depressions 0.1 mV for less than 30 seconds are rare in normal subjects and correlate strongly with myocardial perfusion scans that show regional ischemia.
What have Holter monitors demonstrated about angina and its pattern of occurrence?
Holter monitoring has shown that the majority of ischemic episodes that occur during normal daily activities are silent (asymptomatic) and that symptomatic and silent episodes of ST-segment depression exhibit a circadian rhythm, with ischemic ST-changes more common in the morning. Studies also have shown that nocturnal ST-segment changes are almost always an indicator of two- or three-vessel coronary artery disease or left mainstem stenosis.
Do certain groups of patients benefit from Holter monitoring for detection of silent ischemia?
The answer depends on the clinical picture, but patients with an anginal equivalent and risk factors for coronary artery disease (e.g., exerctional shortness of breath) are also at high risk for ischemia. Patients with type II diabetes mellitus also have a greater incidence of asymptomatic ischemia as well as silent myocardial infarctions and may benefit from Holter evaluation for silent ischemia.