Effect of age on systolic intervals (STI).

Weissler's corrected STI was to be used in the assessment of cardiac performance taking into account only the heart rate and sex. But there are many other determinants of STI, among them an important one is the age. In the present paper, in 422 normal adults (280 men and 142 women) divided according the age into three groups (20-29, 30-39, 40-60 years), we found significant differences concerning STIc with age, especially over 40 years old. On the other hand, in a previous paper we have found in trained athletes similar modifications of STIc as those noticed in cardiac failure. That is why we, like other authors, do not consider Weissler's STIc as valid in the assessment of cardiac performance.

Absence of increased cardiac voltage and the importance of Q vectors for the diagnosis of left ventricular hypertrophy in early stages of hypertension in patients over 40 years of age.

The quantitative VCG criteria (VCGer) for left ventricular hypertrophy (LVH) and their diagnostic power were determined in 165 hypertensive men and 86 women over 40 years of age without congestive cardiac failure in comparison with 91 normal men and 108 normal women. The patients were grouped according to the presence or absence of LVH determined by X-ray (men: 96 without and 69 with LVH, women: 41 without and 45 with LVH). The proper statistical methods were used taking into account whether their distributions were symmetrical or asymmetrical. We found some sex differences of VCG criteria. The most striking results were the lack of increased voltage, and the great sensitivity of the orientation of Q vectors to the left (Q left). Q left may be induced by: 1. a septal hypertrophy, alone or accompanied by a hypertrophy of the anterior and posterior paraseptal regions of LV wall, 2. by a subendocardial ischemia at these levels induced by the increase of intraventricular pressure, 3. by possible spatial change of the septum, 4. by all these factors acting synchronously, 5. by other, unknown factors. These VCGcr for LVH found by us are different from those in the literature, but they are valid in Romania.

New mathematical statistical methods for detecting correct echocardiographic (ECG) and vectorcardiographic (VCG) diagnosis criteria by computerization. I. The determination of the upper (Lu) and low (Ll) limits for VCG amplitudes. The multivariate analysis.

The mathematical statistical methods for the determination of the upper (Lu) and low (Ll) limits of the 95 percentile range of symmetrical and asymmetrical frequency distribution curves for electrocardiographic (ECG) or vectorcardiographic (VCG) amplitudes, ECG and VCG diagnostic criteria, and the multivariate analysis as well as the bases of their computerization-program have been presented, in order to find out the ECG and VCG diagnostic criteria. The formulae for the determination of sensitivity, specificity and performance score of the ECG and VCG diagnostic criteria, in both the above mentioned methods are presented.

Effect of age on the heart electrical phenomena, left ventricular wall thickness and blood pressure in men.

The effect of age on the maximal spatial QRS vector (MSQRSV) in the Frank lead system was correlated with th posterior left ventricular wall thickness (PLVWT), the interventricular septum thickness (IVST) determined by echocardiography, and with blood pressure in 300 normal men, distributed by age groups (20-29, 30-39, 40-60). With advancing age, a significant decrease of MSQRSV accompanied by a significant increase of PLVWT was observed while the increase of IVST and of blood pressures with age were found non significant. It was concluded that: 1. blood pressure is not the sole determinant of hypertrophy; 2. myocardial hypertrophy is not the sole determinant of cardiac voltage increase; 3. there is some degree of myocardial sclerosis in healthy people aged over 40-60 years; 4. in left ventricular hypertrophy the left ventricular muscular mass cannot be accurately predicted from the heart electrical phenomena; 5. the results obtained were in agreement with those of authors describing different aspects of normal Frank ECG and vectorcardiogram (VCG) in subjects under and over 40-50 years of age; 6. the variability of the degree of age influence on normal ECG from one country to another could explain the different diagnostic criteria for the same cardiac disease in computerized programs.

Studies concerning the role of myocardial hypertrophy and of intramural tension as determinants of the increased voltage in concentric left ventricular hypertrophy.

In order to study the role of myocardial hypertrophy and of the intramural tension as determinants of the increased voltage in concentric left ventricular hypertrophy, the amplitude of intracellular action potentials in frog and rat myocardium and of monophasic action potentials recorded in dogs by suction electrodes were studied. Increased amplitudes of intracellular action potentials were seen neither in experimental LVH in rats nor during stretch in frog and rat myocardium. The increased intramural tension in dog heart during norepinephrine perfusion or in heart-lung preparation during increased peripheral resistance does not increase the amplitude of monophasic action potentials. The abrupt hypertension induced by norepinephrine is an inadequate model for the study of the effect of increased intramural tension. The increase of the voltage in LVH cannot be accounted for by the increase of action potentials of each hypertrophied fibre. Many factors cooperate in producing increased voltage of LV in LVH.

Studies concerning the significance of orthogonal ECG changes with age in normal men and in arterial hypertension without congestive cardiac failure in men past forty.

Great ECG changes (Frank system) with age were found in normal men. ECG diagnostic criteria valid in Romania were studied by multivariate analyses in men aged 40--60 suffering from hypertension (Hyp) without cardiac congestive failure (CCF), out of which one group with left ventricular hypertrophy (LVH) and another one without it. Echocardiographic studies in normal and hypertensive men past forty, as well as studies in experimental Hyp with LVH and without CCF were carried out. Heart X-ray evaluation is not a functional one. Some non-invasive methods in men do not determine an accurate evaluation of LV performance. The increase of LV muscular mass alone cannot explain the ECG changes in LVH in Hyp without CCF. Two conditional adaptive mechanisms: the liberation of catecholamines from the myocardium storage, induced by the pressure overload stress, and the increase of intracellular Ca++ influx could contribute to the respective ECG changes.

The role of increased Ca++ influx as a possible additional adaptive mechanism in experimental left ventricular hypertrophy (exp LVH).

Membrane potentials, isometric contraction and autohistoradiography with 45Ca in papillary muscle of rats with experimental LVH without cardiac failure as compared with sham-operated animals proved an increased Ca influx per beat and a Ca accumulation at or near the sarcolemma. This phenomenon is regarded as an additional mechanism for the improvement of the cardiac performance in the compensatory stage of the experimental LVH without cardiac failure.