* Member of ACP-ASIM and ISIM
INTRODUCTION:
The importance of resting heart rate as a cardiovascular risk
factor has been increasingly recognized since the studies of Framingham
and Göteborg, reinforced by the success of Betablockers in
coronary heart disease, congestive heart failure and perioperative
mortality in high risk patients. Recently, heart rate variability,
chronotropic incompetence and heart rate recovery after exercise,
have demonstrated to be predictors of mortality. In all mammals,
the slower the pulse, the longer the lifespan, and viceversa.
At the other hand, obesity is already
recognized as a major cardiovascular risk factor. Years ago, we
observed an apparent relation of 3:1 (72:24) between resting heart
rate and body mass index. Then we developed the Pulse×Mass
Index and compared it both with the studies on obesity and
mortality and with the calculation of the global cardiovascular
risk according to Framingham. [1]
The Pulse×Mass Index reflects
overweight, stress, sympathetic stimulation, oxidative metabolic
rate, hyperinsulinemia, inflammatory activity, physical fitness
and side effects of drugs like water retention, potent vasodilation
and tachycardia. The therapeutic interventions or lifestyle modifications,
should improve the treated cardiovascular risk factor without
increasing, or better reducing Pulse×Mass Index, while,
if possible, improving chronotropic incompetence and heart rate
recovery.
Based on our investigations, a Pulse×Mass
Index of 0.7-1.0 would be ideal.
Pulse×Mass Index = Resting Heart
Rate ×Body Mass Index 1730 [or 72 × 24]
METHODS:
In a pilot group of 34 patients, we compared Pulse×Mass
Index [percent in excess over 1.0, e.g. 1.30 = 30% in excess]
with the calculation of the global cardiovascular risk according
to Framingham (known tabulation based on age, sex, smoking, diabetes,
left ventricular hypertrophy, systolic blood pressure, total and
HDL cholesterol: a global risk of 30% of events in 10 years is
very significant). We also compared Pulse×Mass Index
with the real, empirically observed mortality in several studies
with obese, respectively physically fit patients. If both resting
heart rate and body mass index were given, we calculated the real
Pulse×Mass Index. If only body mass index was given,
we assumed a 3:1 relation between resting heart rate and body
mass index and calculated a theoretical Pulse×Mass Index,
then compared it with the mortality.
RESULTS AND CONCLUSIONS: After comparing the pulse×mass index with the global cardiovascular risk according to Framingham, we found a highly significant correlation (r=0.95; n=34; p<0.05), especially in patients over 40 years, despite the pulse×mass index being more sensitive for younger patients. (see figure).
When we calculated and compared pulse×mass index with the real observed mortality in the study by Erikssen et al. (Norway, 1998), who followed about 2000 physically fit patients for 22 years, we found a surprisingly similar result, applying their own data:
for an increase of 1 S.D. in resting heart rate (10.1 bpm) plus an increase of 1 S.D. in body mass index (2.7 kg/m2), they had a combined mortality of 1.28 (28% in excess).
The real calculated pulse×mass
index is 1.27=[(72+10.1=82.1)×(24+2.7=26.7)÷1730]
suggesting that pulse×mass index can be predictive
of mortality. [2]
Moreover we also observed, analyzing studies on obesity and mortality, that if the relation of 3:1 between pulse and body mass index was maintained proportional as body mass index increases, then the enlarged mortality becomes predictable -e.g., for a body mass index of 33 and a theoretically corresponding pulse of 99 (1/3), the pulse×mass index (33×99÷1730) is 1·9 or almost two-fold, corresponding with the known doubling of mortality by this body mass index. The same tendency is found for every increase of body mass index and pulse, although, as suspected, the mortality tend to be higher in younger obese men. [3]
Interestingly, in a recent study, the
group of Cole and Lauer found an increased mortality in the patients
with abnormal heart rate recovery after excercise. When we calculated,
using their own data, the pulse×mass index of this
patients, it resulted to be 1.28, which corresponds to
a high risk group. Moreover, the real relation of resting heart
rate to body mass index was about 3 to 1, in both, the normal
and abnormal groups. [4]
In other recent studies on obesity and mortality from Calle et al. in USA (over one million patients observed during 14 years), and Bender et al. in Germany (over 6000 obese patients observed during 15 years, average body mass index [BMI] of 36.6 and age 40 years), if we calculate the theoretical pulse×mass index, assuming a relation of 3:1 between resting heart rate and body mass index, we find similar results: [5], [6]
Bender: BMI = 36.6, real mortality increased to = 2.0 [ theoretical pulse×mass index = 2.3 ]
Calle: male, BMI 35, real mortality increased to = 2.0 [ theoretical pulse×mass index = 2.1 ]
male, BMI 40, real mortality increased
to = 2.7 [ theoretical pulse×mass index = 2.8 ]
Thus, pulse×mass index, a widely accessible index of physical signs, appears to be predictive of both cardiovascular risk and mortality, and can contribute together with the known risk factors, to a more complete assessment of cardiovascular risk. It should be done routinely in every patient.
Refs:
Dr. Enrique Sánchez-Delgado, and Heinz Liechti, M.Sc.
Laboratorios Solka S.A., P.O. Box A-02, Managua, Nicaragua,
Tel. 00505-278-1031; Fax. 00505-270-3819 and 279-9653
E-mail: solka@ibw.com.ni
http://www.geocities.com/ciencia_farma