Holter recordings

Measurement of QT interval Definition of the end of the T wave. Changes in T wave morphology and occurrence of U waves (these may be important warning signs and precede the occurrence of TdP) Errors in manual measurement in QT interval Variability in the heart rate (need to correct the QT value for heart rate) Lack of reliable correlation between readings from Holter recordings and standard ECG Lack of standardization of automated ECG readings (computerized methods are often unreliable) Need for a central core laboratory to analyze data... 

A healthy 32-year-old doctor, who smoked marijuana 1-2 times a month, had paroxysmal tachycardia for several months. An electrocardiogram was normal and a Holter recording showed sinus rhythm with isolated supraventricular extra beats. He was treated with propranolol. He later secretly smoked marijuana while undergoing another Holter recording, which showed numerous episodes of paroxysmal atrial tachycardia and atrial fibrillation lasting up to 2 minutes. He abstained from marijuana for 12 months and maintained stable sinus rhythm. 

In a randomized, double-bhnd, placebo-controlled study in 32 patients with ventricular extra beats (more than 30/hour on two consecutive 24-hour Holter recordings while drug free and more than 50/hour during 2-hour telemetric electrocardiography), dofetihde 7.5 micrograms/kg produced an 83% and placebo a 2.9% median reduction in ventricular extra beats (49). 

Lupoglazoff JM, Denjoy I, Berthet M, Neyroud N, Demay L, et al. 2001. Notched T waves on Holter recordings enhance detection of patients with LQT2 (HERG) mutations. Circulation 103 1095-101... 

Figure 4.1 Holter recording of a very young patient with early repolarisation pattern recorded at night (A) that disappeared at daytime (B). During tachycardia the repolarisation presents changes typical of sympathetic overdrive (C).

Figure 8.11 Holter recording of a patient with a severe crisis of Prinzmetal angina. Observe the presence of clear ST-segment and TQ alternance together with some PVC.

The presence of PVCs, especially of the R on T type, may represent a real risk of sudden death due to VF during the acute phase of ischaemia. In post-infarction patient, when PVCs are found in a surface ECG of 1- or 2-minute duration, this generally implies that PVCs will be frequent in the Holter recording, which has prognostic implications (Bigger et al., 1984). 

Homs E, Marti V, Guindo J et al. Automatic measurement of corrected QT interval in Holter recordings comparison of its dynamic behavior in patients after myocardial infarction with and without life-threatening arrhythmias. Am Heart J 1997 134 181. 

Note. Technical specifications were omitted here due to the multiplicity of parameters. The reader is referred to the manufacturers information outlets (e.g, Internet homepages). Ambulant ECG (Holter) recorder, ambulatory blood pressure monitors, and sleep apnea recorders were not included. 

Fig. 10.4 Representative Holter recordings from an asymptomatic patient with a type I block variant that was misdiagnosed as type II block by several physicians. (A) Type I block with constant PR intervals before the blocked beat. Note that there is a slight increase in the sinus rate in the seqnence before the blocked beat. However, the sinus rate then slows down and the blocked P-wave occurs in association with sinus slowing a combination consistent with a vagal phenomenon. The PR intervals after the blocked beat are inconstant. (B) Type I variant simulating type II block. The PR intervals are constant before and after the blocked beat. However, there is obvious sinus slowing simultaneously with the nonconducted P-wave. (C) Type I block. Note that in the presence of a narrow QRS complex, the occurrence of type I (with fairly large increments of the PR intervals) and what appears to be type II block basically rules out the presence of a true type II block.

When confronted with a pattern that appears to be type II with a narrow QRS complex (especially in Holter recordings), one must consider the possibility of type I block without discernible or measurable increments in the PR... 

Novak M, Smola M, Kejrova E, Pacemaker built-in Holter counters match up to ambulatory Holter recordings. In Sethi KK (ed) Proceedings of the Vlth Asian-Pacific Symposium on Cardiac Pacing and Electrophysiology, Bologna, Italy, Monduzzi Editore S.p.A., 1997 61-64. 

After acute PSVT is terminated, long-term preventive treatment is indicated if frequent episodes necessitate therapeutic intervention or if episodes are infrequent but severely symptomatic. Serial testing of antiarrhythmic agents can be evaluated in the ambulatory setting via ambulatory ECG recordings (Holter monitors) or telephonic transmissions of cardiac rhythm (event monitors) or by invasive electrophysiologic techniques in the laboratory. 

Figure 3.11 Tall and peaked T wave not secondary to ischaemic heart disease recorded at night (Holter) in a sportsman with vagal overdrive. Note the significant bradycardia, the asymmetric T wave and the slight ST-segment elevation (early repolarisation). There is a...

Figure 8.10 Patient with crises of Prinzmetal angina, who presented during these crises typical of subepicardial injury pattern. During the remission of pain (Holter method recording) the injury pattern disappeared within a few seconds.

Figure 8.34 Patient of 68 years of age who suffered sudden death 10 days after an acute infarction. A progressive depression of the automatism (with the appearance of a slow escape rhythm) is shown in the Holter ECG recording, until cardiac arrest occurs, due to an electromechanical dissociation caused by cardiac rupture.

Figure 8.46 Above Crisis of coronary spasm (Prinzmetal angina) recorded by Holter ECG. (A) Control. (B) Initial pattern of a very tall T wave (subendocardial ischaemia). (C) Huge pattern of ST-segment elevation. (D-F) Resolution towards normal values. Total duration of the crisis was 2 minutes. Below Sequence of a crisis of Prinzmetal angina with the appearance of ventricular tachycardia runs at the moment of maximum ST-segment elevation.

Figure 12.2 During Holter monitoring in a patient with ischaemic heart disease, crises often silent with ST-segment elevation or depression may be recorded.

Phenol in aqueous solution is absorbed very differently to phenol in oil solution. Maximum blood levels reached 0.9 mg/100 ml when phenol was applied in an oil solution and 1.1 mg/100 ml in an aqueous solution. In 1950, Deichmann" published a study on the reabsorption of phenol in an aqueous and an oil vehicle 71 mg of phenol was absorbed by the skin of a rat in 1 hour s contact with an aqueous solution of phenol at 4.7%, whereas only 15 mg was absorbed when the same concentration was present in (mineral) oil solution. Phenol penetrates the skin more slowly from an oil solution than from an aqueous solution. In this way, it also becomes less toxic. Applying 4 g of phenol to the skin does not make the blood concentration of the free form or conjugated form of phenol any higher than if 3 g were applied. Deichmann did not offer any explanation of this phenomenon, but the rest period of 90 minutes between each 1 g application most probably allowed enough time for the phenol to be detoxified. After 3 g, the phenol levels returned to normal within 48 hours. A little longer was needed to eliminate 4 g. On the third day, the blood levels of phenol reached doses lower than that of any normal individual, that is, around 0.15 mg. No sign of systemic intoxication was detected in the course of this study. It must be noted, however, that control mechanisms were not as sophisticated as they are today and continuous Holter-ECG recording monitors were, for example, not yet available then. 

Reiffel JA, Bigger JT, Jr., Cramer M, Reid DS. Ability of Holter electrocardiographic recording and atrial stimulation to detect sinus nodal dysfunction in symptomatic and asymptomatic patients with sinus bradycardia. Am J Cardiol. 1977 40 189-194. 

Conventional ECGs would have to be replaced by high-resolution 12-lead Holter ECG recordings. 

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