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A NEW AXIS-DEVIATION CALCULATOR
364 been known to pathologists for a long time. Arterial calcification increases of course with the higher age-groups, but in our last series of 2000 examinations calcification in the common iliac arteries, as evidence of beginning vascular degeneration, was found in 2% of the 40-49 age-group. There appears to be a correlation between calcification in the common iliac arteries and an unfavourable electrocardiogram which would be of particular importance in this age-group. With the help of a computer, the radiological findings in relation to other clinical tests are now
being worked
Institute of Directors Medical London, S.W.1.
out.
Centre,
HENRY W. GILLESPIE.
TETANUS: A DILEMMA PROLONGED
SIR,-ln your leading article (Jan. 29)
no
reference is made
antitetanus serum testing sensitivity patients (A.T.S.), or to giving this serum in divided doses. It would be interesting to know what effect this procedure might have on the estimated 22 deaths a year that would be likely to occur in Great Britain if the serum were given to every patient with a wound that required prophylactic therapy. Since desensitisation is an important procedure, in connection with the giving not only of A.T.S. but of all non-human serum, I should have thought that it would have merited consideration along with the other factors you so rightly mention. Streetly, Sutton Coldfield, T. K. ELLIOTT. Warwickshire.
to
the
of
for
to
A NEW AXIS-DEVIATION CALCULATOR
SiR,-The axis-deviation calculator suggested by Dr. Milledge1 appears cumbersome for estimating mean electrical axis. Rather than simply taking the magnitude of deflection in the frontal leads in order to determine the mean QRS axis, it is well established that one should attempt to integrate the area under the QRS deflections to obtain a more accurate estimation of QRS axis.2-4 In practice, the measured height of R waves and depth
least deflection in the lead to which it is perpendicular. That is, one may say that the vector is at right angles to the lead in which the QRS complex is diphasic (or isoelectric). By determining the general direction (right or left, up or down) of the mean QRS vector and then estimating the axis from a standard frontal reference frame (fig. 1), the clinician can (without pencil, paper, or mechanical calculator) quickly calculate the mean electrical axis. In the example (fig. 2), the QRS complex is predominantly positive in leads I and in and is diphasic in a VL. The mean vector therefore is directed down and to the left at an angle of about +60°. The T-wave vector can be determined similarly. In the example it is about +30°. With practice, the QRS and T axes can be quickly and accurately determined without the use of mechanical calculators. Department of Medicine, St. Luke’s Hospital Center, New York, New York 10025, PETER H. GOTT. U.S.A.
MIGRAINE SIR,-Dr. Stanford1 shows the importance that can still be attached to clinical observation. She gives an excellent account of premenstrual migraine, with attacks associated constantly with the menstrual cycle, occurring regularly at ovulation or on the first day of the period, with noticeable oliguria during the attack and polyuria heralding its end, and with a rise of bloodpressure at the onset. It is indeed a classical example. There are many types of migraine and many causes, and it is important to recognise the types which respond to treatment. The response of premenstrual migraine to progesterone injections is most gratifying. The aetiology of premenstrual syndrome is not yet fully understood, nor is the mechanism by which progesterone relieves sufferers,2 but the fact that it does bring relief and normality back to a patient’s life constrains the clinician to treat-and to leave to greater brains the solution of this aaiological problem. KATHARINA DALTON
MEASURING GLOMERULAR FILTRATION-RATE
SiR,-Your leading article3 drew attention
to a preliminary Slapak and Hume 4 describing a method of measuring glomerular filtration-rate (G.F.R.) with labelled vitamin B12’ This method was based on a diminishing blood-
communication by
r uyr
Fig. 1-Standard frontal reference frame for determining electrical axis of QRS complex.
Fig. 2-Electrocardiogram with QRS complex which is dominantly positive in leads I and III, and is diphasic in
prea
VL.
ofs waves suffice to estimate, within 15°, a fairly accurate mean electrical axis. The mean QRS vector will produce the greatest deflection in the electrocardiographic lead to which it is parallel and the 1. Milledge, J. S. Lancet, 1965, ii, 954. 2. Grant, R. P. Clinical Electrocardiography; p. 13. New York, 1957. 3. Massie, E., Walsh, T. J. Clinical Vectorcardiography and Electro cardiography; p. 38. Chicago, 1960. 4. Corne, R. A., Parkin, T. W. Proc. Staff Meet. Mayo Clin. 1965, 40, 901
concentration of B12 without collection of urine. In their example illustrated in fig. 1, Slapak and Hume have computed the slope (m) of the exponential plasma-clearance curve using logarithms to the base 10. It is, however, inadmissible to substitute the value thus derived into the relation C = mV (where C = the clearance rate, and V = the volume from which the tracer is cleared) as is done in their communication. If on the other hand the slope of the line in their fig. 1 is calculated by Napierian logarithms (or alternatively from the simple relation m=log e2/t1/2, where tt is the time taken for the plasmaconcentration to fall to one half its initial value), the value obtained is 0-0094 min.-1 (i.e., 2-3 x 0.00408), and the conclusion that the plasma-concentration falls by 0-94% per minute accords well, as it should, with what may be immediately observed from inspection of the graph. Substituting this value into the clearance formula, the correct value for the clearance in the experiment exemplified in fig. 1 is 225 ml. per minute. In our own experience with vitamin B, 2, equilibration through the body B12 space is not reached within 90 minutes of injection, and the fall in plasma-radioactivity within this time (as has already been pointed out by Aurell 5) doubtless reflects processes other than glomerular filtration alone. It is possible that utilisation of the cortion of the curve between 20 and 50 Stanford, E. Lancet, 1965, ii, 1346. Dalton, K. The Premenstrual Syndrome. London, 3. Lancet, 1965, ii, 276. 4. Slapak, M., Hume, D. M. ibid. 1965, i, 1095. 5. Aurell, M. ibid. 1965, ii, 188. 1. 2.
1964.
being worked
Institute of Directors Medical London, S.W.1.
out.
Centre,
HENRY W. GILLESPIE.
TETANUS: A DILEMMA PROLONGED
SIR,-ln your leading article (Jan. 29)
no
reference is made
antitetanus serum testing sensitivity patients (A.T.S.), or to giving this serum in divided doses. It would be interesting to know what effect this procedure might have on the estimated 22 deaths a year that would be likely to occur in Great Britain if the serum were given to every patient with a wound that required prophylactic therapy. Since desensitisation is an important procedure, in connection with the giving not only of A.T.S. but of all non-human serum, I should have thought that it would have merited consideration along with the other factors you so rightly mention. Streetly, Sutton Coldfield, T. K. ELLIOTT. Warwickshire.
to
the
of
for
to
A NEW AXIS-DEVIATION CALCULATOR
SiR,-The axis-deviation calculator suggested by Dr. Milledge1 appears cumbersome for estimating mean electrical axis. Rather than simply taking the magnitude of deflection in the frontal leads in order to determine the mean QRS axis, it is well established that one should attempt to integrate the area under the QRS deflections to obtain a more accurate estimation of QRS axis.2-4 In practice, the measured height of R waves and depth
least deflection in the lead to which it is perpendicular. That is, one may say that the vector is at right angles to the lead in which the QRS complex is diphasic (or isoelectric). By determining the general direction (right or left, up or down) of the mean QRS vector and then estimating the axis from a standard frontal reference frame (fig. 1), the clinician can (without pencil, paper, or mechanical calculator) quickly calculate the mean electrical axis. In the example (fig. 2), the QRS complex is predominantly positive in leads I and in and is diphasic in a VL. The mean vector therefore is directed down and to the left at an angle of about +60°. The T-wave vector can be determined similarly. In the example it is about +30°. With practice, the QRS and T axes can be quickly and accurately determined without the use of mechanical calculators. Department of Medicine, St. Luke’s Hospital Center, New York, New York 10025, PETER H. GOTT. U.S.A.
MIGRAINE SIR,-Dr. Stanford1 shows the importance that can still be attached to clinical observation. She gives an excellent account of premenstrual migraine, with attacks associated constantly with the menstrual cycle, occurring regularly at ovulation or on the first day of the period, with noticeable oliguria during the attack and polyuria heralding its end, and with a rise of bloodpressure at the onset. It is indeed a classical example. There are many types of migraine and many causes, and it is important to recognise the types which respond to treatment. The response of premenstrual migraine to progesterone injections is most gratifying. The aetiology of premenstrual syndrome is not yet fully understood, nor is the mechanism by which progesterone relieves sufferers,2 but the fact that it does bring relief and normality back to a patient’s life constrains the clinician to treat-and to leave to greater brains the solution of this aaiological problem. KATHARINA DALTON
MEASURING GLOMERULAR FILTRATION-RATE
SiR,-Your leading article3 drew attention
to a preliminary Slapak and Hume 4 describing a method of measuring glomerular filtration-rate (G.F.R.) with labelled vitamin B12’ This method was based on a diminishing blood-
communication by
r uyr
Fig. 1-Standard frontal reference frame for determining electrical axis of QRS complex.
Fig. 2-Electrocardiogram with QRS complex which is dominantly positive in leads I and III, and is diphasic in
prea
VL.
ofs waves suffice to estimate, within 15°, a fairly accurate mean electrical axis. The mean QRS vector will produce the greatest deflection in the electrocardiographic lead to which it is parallel and the 1. Milledge, J. S. Lancet, 1965, ii, 954. 2. Grant, R. P. Clinical Electrocardiography; p. 13. New York, 1957. 3. Massie, E., Walsh, T. J. Clinical Vectorcardiography and Electro cardiography; p. 38. Chicago, 1960. 4. Corne, R. A., Parkin, T. W. Proc. Staff Meet. Mayo Clin. 1965, 40, 901
concentration of B12 without collection of urine. In their example illustrated in fig. 1, Slapak and Hume have computed the slope (m) of the exponential plasma-clearance curve using logarithms to the base 10. It is, however, inadmissible to substitute the value thus derived into the relation C = mV (where C = the clearance rate, and V = the volume from which the tracer is cleared) as is done in their communication. If on the other hand the slope of the line in their fig. 1 is calculated by Napierian logarithms (or alternatively from the simple relation m=log e2/t1/2, where tt is the time taken for the plasmaconcentration to fall to one half its initial value), the value obtained is 0-0094 min.-1 (i.e., 2-3 x 0.00408), and the conclusion that the plasma-concentration falls by 0-94% per minute accords well, as it should, with what may be immediately observed from inspection of the graph. Substituting this value into the clearance formula, the correct value for the clearance in the experiment exemplified in fig. 1 is 225 ml. per minute. In our own experience with vitamin B, 2, equilibration through the body B12 space is not reached within 90 minutes of injection, and the fall in plasma-radioactivity within this time (as has already been pointed out by Aurell 5) doubtless reflects processes other than glomerular filtration alone. It is possible that utilisation of the cortion of the curve between 20 and 50 Stanford, E. Lancet, 1965, ii, 1346. Dalton, K. The Premenstrual Syndrome. London, 3. Lancet, 1965, ii, 276. 4. Slapak, M., Hume, D. M. ibid. 1965, i, 1095. 5. Aurell, M. ibid. 1965, ii, 188. 1. 2.
1964.