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3. Richard F. ohnell. Some PQ problems Sloping PQ segment, Wenckebachs periods, pre-excitation. (Reuiew) 1. A gently rising PQ-segment may apparently be a normal occurence, due to auricular activity, but some of these electrocar- diograms are due to pre-excitation. OHNELL 1944, p. 49; id. 1945 reports such cases and others have been observed lately. The slope of the PQ segment is perhaps 1-1.5 mV/Sec. The task is to diffe- rentiate pre-excitation from non-pre-excitation. To the possibilities of establishing or rejecting the pre-excita- tion diagnosis, submitted by the author (id. 1944, 1945, 1948), we here add a simple criterion which has proved of practicable significance: Fig. 1. sketches two different alternatives. The dofted PQ- segment does not reach above the isoelectric line, while the con- tinuour one lies above this level. In the former case the PQ segment may form part of the normal electrocardiogram, while in the latter case an additional wave of ventricular excitation (pre-excitation) is probably present. 1948, OHNELL 1947). Table 1 breafly states a few characteristics from three eases. After slight physical activity in all three cases the Wenckebach periods disappeared and the PQ became normal. Case 1 disclosed a particularly interesting phenomenon, viz., a dropped ventricular beat at each breath, largely independent of the respiratory frcquencp. 2. Wenckebnch periods: (Cp. OHNELL and ANDERSSON 1946,

Some PQ problems : Sloping PQ segment, Wenckebachs periods, pre-excitation

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Page 1: Some PQ problems : Sloping PQ segment, Wenckebachs periods, pre-excitation

3. Richard F. ohnell.

Some PQ problems

Sloping PQ segment, Wenckebachs periods, pre-excitation.

(Reuiew)

1. A gently rising PQ-segment may apparently be a normal occurence, due to auricular activity, but some of these electrocar- diograms are due to pre-excitation. OHNELL 1944, p. 49; id. 1945 reports such cases and others have been observed lately. The slope of the PQ segment is perhaps 1-1.5 mV/Sec. The task is to diffe- rentiate pre-excitation from non-pre-excitation.

To the possibilities of establishing or rejecting the pre-excita- tion diagnosis, submitted by the author (id. 1944, 1945, 1948), we here add a simple criterion which has proved of practicable significance:

Fig. 1. sketches two different alternatives. The dofted PQ- segment does not reach above the isoelectric line, while the con- tinuour one lies above this level. In the former case the PQ segment may form part of the normal electrocardiogram, while in the latter case an additional wave of ventricular excitation (pre-excitation) is probably present.

1948, OHNELL 1947). Table 1 breafly states a few characteristics from three eases. After slight physical activity in all three cases the Wenckebach periods disappeared and the PQ became normal. Case 1 disclosed a particularly interesting phenomenon, viz., a dropped ventricular beat a t each breath, largely independent of the respiratory frcquencp.

2 . Wenckebnch periods: (Cp. OHNELL and ANDERSSON 1946,

Page 2: Some PQ problems : Sloping PQ segment, Wenckebachs periods, pre-excitation

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Case 1. 1 Case. 2.1 Case. 3.

Original diagnosis Wenckebach periods

After physical activity

Possible transitional stage Prolonged PQ time (Sino-auricular block)

l- I l-

Normal PQ time

- (One P T complex mis- sed every second breath)

One QT missed ICorrelation with breathing each breath

Fig. 1.

Fig. 2.

Page 3: Some PQ problems : Sloping PQ segment, Wenckebachs periods, pre-excitation

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It is possible that certain cases of what look like Wenckebach periods should rather be interpreted as due to increased autonomic inhibition, varying with the rcspiration, than as due to insufficient restauration from one beat to the other.

3. The diagnosis of pre-excitation often difficult. On? of the problems encountered was entered upon above.

The cstablishment of the diagnosis may sometimes require hours, days or even weeks (Cp. OHNELL 1948).

Fig. 2 shows at upper left two cases of pre-excitation where a cursory glance at the electro-cardiogram would not suggest the diagnosis. The othcr two examples derive from Don-pre-excitation cases, where the curve might easily be mistaken for pre-excitation.

, It is essential that the investigator ask himself the following question: 'is an additional excitatory spead present, coupled t o auricular activity and causing a slighly premature excitation in the region where i t spreads?'

References

OAKELL, R. P.: Acta Med. Scand. Suppl. 152, 1944. OHYELL, R. F.: Nord. Med. 25:220:1945. OHNELL, R. F.: Llecture in the Physiol: SOC. Stockholm 1947 (to be

OANELL, R. F.: $The cardiological ternis pre-excitation . , (with summary

OHNELL, K. F. and ANDERSSON, Bo: Svenska Lakartidningen 43:1777:

OHNELL, R. F. and ANDERSSON, Bo: Cardiologia 1231948, fasc. 415 1948.

printed).

in english) Nord. Med. 1948 (in print).

1946.