331Subendocardial Infarction. The criteria mentioned above were used. In both subepicardial and subendocardial infarction a progressive reduction of the height of the R wave also occurred frequently. CRITERIA FOR LOCATION OF TRANSMURAL INFARCTION(1) Diaphragmatic Infarction.-A Q wave of >0 04 sec in aVF and >25% of the amplitude of R in aVF; a Q wave of >0 03 sec and ST-T evolution in aVF, typical of myocardial infarction. An increase in the Q duration in aVF with at least 0-02 sec with typical ST-T segment changes, in the presence of a Q wave in L2 of >0 02 sec. The appearance of Q wave in L3 >5mm deep and >0 04 sec duration in the presence of an R wave in L3 >1 mm (without a pathological Q wave in aVF). A Q wave of >0-05 sec and >33%' of the R wave in aVF in the presence of a complete left bundle-branch block.(2) Posterolateral Infarction.-A Q wave >0 03 sec. Q wave >0-02 sec plus typical sequential ST-T segment changes and an R loss of >1/3 in V6 (only V6 was used in the evaluation, since more lateral leads were not available in the electrocardiograms from some centres). The conduction disturbances noted were: A-V block first degree, A-V block second degree, A-V block third degree, complete A-V block, complete right bundle-branch block, and complete left bundle-branch block; left parietal block (R/S <05 in L2 in the absence of an S wave in a VL and a QRS duration <0-12 sec); and right parietal block (terminal R wave Vl of at least 1 mm, with QRS duration <0-12 sec). RHYTHM DISTURBANCESRhythm disturbances noted were nodal rhythm, auricular fibrillation, auricular flutter, paroxysmal auricular tachycardia, and ventricular tachycardia.

Summary: Plasma levels of tricyclic antidepressant drugs vary considerably between individuals receiving the same amount of drug. The bearing of this variation on the occurrence of subjective side effects was investigated in 40 psychiatric inpatients with depressive disorders. Plasma levels were determined before and during four weeks of treatment with nortriptyline 50 mg. three times a day and patients were rated for subjective side effects, the assessors being unaware of the plasma levels of the drug.Plasma levels varied widely between individual patients, but in any given patient the plasma level tended to be constant over a period of time. The side effects of nortriptyline diminished significantly with time and were in most cases absent during the fourth week of treatment. There was a significant positive correlation between plasma level of nortriptyline and subjective side effects. The steady-state plasma level of a drug which is metabolized is usually a more important determinant for its effect than dosage, since it reflects the amount of drug available for biological action. Very high plasma levels of nortriptyline should presumably be avoided, since there is no evidence that they are needed for therapeutic effect and they are potentially harmful.

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