Diastolic time during exercise in normal subjects and in patients with coronary artery disease. A plethysmographic study

Percent diastole (%D) was evaluated at rest and during effort (submaximal upright exercise) in 13 normal subjects and in 14 age-matched patients with coronary artery disease (CAD). Systolic time intervals were also simultaneously recorded by using the thermistor pulse transducer. At rest, in both groups, a positive linear regression was found between %D and cycle length (RR) (%D = 19.1 + 0.044RR, r = 0.83 in normals; %D = 21.2 + 0.044RR, r = 0.88 in CAD). During effort, while in normals no correlation was found between %D and RR values, in CAD patients %D and RR were linearly related (%D = -12.81 + 0.087RR, r = 0.67). These results prove that diastolic time is differently affected by the exercise in the two examined groups and that in CAD patients an abnormal reduction of %D occurs during stress test.

Effect of experimental infarct on the mortality rate in alloxan-diabetic rats

The authors report the wide mortality observed in alloxan diabetic rats infarcted with large doses of isoproterenol. The experimental data are in line with the results of clinical studies testifying that the diabetic disease involves the cardiovascular system and affects the prognosis of myocardial infarct. These experiences do not permit to define the direct mechanism(s) responsible for the high mortality in diabetic infarcted rats over controls (diabetic not infarcted); however these results give rise to a discussion on the following topics: 1. The damage of intramural coronary vessels as a cause of depressed cardiac contractility in diabetic rats. 2. The role of reduced plasmatic levels of insulin in depressing myocardial performance in alloxan diabetic rats. 3. The hyperglycaemia-provoking effect of isoproterenol as a contributing factor in the death of diabetic rats. 4. The possible direct action of diabetogenic doses of alloxan on the myocardium.

Cardiac hypertrophy in the absence of pressure overload: an experimental and clinical report

A stimulated altitude of 7000 m was applied in rats chronically exposed to hypoxia in a hypobaric chamber. In these experimental conditions the contralateral ventricle not exposed to pressure overload (that is, the left) showed a significant degree of hypertrophy. The hypoxic stimulus did not affect systemic artery pressure or the heart rate. Chronic adrenergic stimulation performed in the rat treated with low doses of isoprenaline (a direct stimulating adrenergic drug) or with tyramine (primarily a releaser of endogenous catecholamines) induced hypertrophy of the right ventricle, left ventricle, and interventricular septum without modifying the haemodynamic parameters mentioned above. The development of ventricular hypertrophy in the absence of pressure overload is stressed. A role for neurohumoral factors (that is, adrenergic stimulation and catecholamines) in the development of ventricular hypertrophy is suggested.

Anterior S-T changes during acute inferior myocardial infarction

We investigated the clinical course of 57 patients with acute inferior myocardial infarction as regards anterior S-T segment depression. Thirty of them showed S-T segment depression greater than or equal to 0.15 mV in at least 2 precordial leads, and 27 did not exhibit such changes. Twenty-seven patients underwent post-infarction exercise stress test. Furthermore, coronary arteriographic findings and left ventricular performance were evaluated in 8 of these patients with and in 8 without anterior S-T segment depression. Patients with anterior S-T segment depression showed greater inferior S-T segment elevation on admission ECG and deeper Q wave in lead aVF in ECG tracings recorded 1 month later. Higher incidences of in-hospital angina (10/30 vs 2/27, P = 0.01) and of late development of cardiac failure (5/21 vs 0/19, P = 0.03) were found among patients with anterior S-T segment depression. They showed a higher overall coronary score (82.4 +/- 31.0 vs 32.5 +/- 28.9, P = 0.002) and left anterior descending artery score (44.1 +/- 20.7 vs 8.5 +/- 16.1, P = 0.0009) and a reduced ventricular performance, evaluated by ventriculography score (49.5 +/- 2.7 vs 51.8 +/- 2.4, P = 0.05). A higher incidence of mitral regurgitation, secondary to papillary muscle dysfunction, was also found among patients with anterior S-T segment depression (4/8 vs 0/8, P = 0.04). Furthermore, the degree of anterior S-T segment depression in each of these subjects was closely correlated with the corresponding difference from normal ventricular score (r = 0.86, P less than 0.01). Finally, no difference between the two groups of patients was found as to incidence of positive exercise stress tests.

Orthostatic hypotension due to autonomic dysfunction--different therapeutic effects of propranolol

In two patients with orthostatic hypotension, due to autonomic dysfunction, hemodynamic changes induced by the assumption of erect position have been evaluated before and during chronic propranolol treatment. Under control conditions, the change in posture induced in Patient 1 a fall in systolic and diastolic blood pressure by 51.4 and 30.7%, respectively. Cardiac output was reduced by 26.8% and systemic vascular resistance by 23.3%. During propranolol treatment, systolic pressure decreased only by 28% and diastolic pressure by 7.7%. The decline in systemic vascular resistance on standing was abolished, while the reduction in cardiac output remained unmodified. In Patient 2, symptoms of orthostatic hypotension were related to marked decrease in systolic blood pressure, the diastolic pressure remaining unchanged. Moreover, systemic vascular resistance increased and, thus, orthostatic hypotension was exclusively dependent upon the severe fall in cardiac output on standing. As a consequence, propranolol failed to control orthostatic hypotension in this patient. These data suggest that when orthostatic hypotension is secondary to failure in peripheral vasoconstriction, propranolol may act beneficially. When it is secondary to a fall in cardiac output, beta-blockade is ineffective.

Beneficial effect of papaverine plus raubasine in peripheral arterial insufficiency

It has been demonstrated that, in most arteriopathic patients, vasodilators induce the vascular steal phenomenon, i.e. the shunting of blood from the ischemic to the normally perfused areas. It is conceivable, therefore, that vasoconstrictors may improve in the opposite way, reducing the blood flow to the normal zones and increasing it to the ischemic. A "reverse vascular steal" caused by the simultaneous IV injection of a vasodilator and a beta-blocker has been previously shown; however, the chronic treatment of arteriopathic patients with beta-adrenoceptor blocking drugs often results in increased evidence of peripheral arterial insufficiency; therefore, the combination of a vasodilating drug with a beta-blocker is limited in the clinical practice. The aim of this study was to investigate the efficacy of the combination of the vasodilator papaverine hydrochloride with a drug having vasoconstrictive action without the undesirable side effects of beta-blockers. Accordingly, raubasine (40 mg) was given p.o. associated with papaverine (300 mg) in 10 arteriopathic patients, who presented a significant reduction of blood flow in the affected limb after the administration of 300 mg p.o. of papaverine alone. The measurements of blood flow were performed by impedance plethysmographic recordings to evaluate papaverine plasma concentrations. Data obtained by this study indicate that papaverine alone induces a significant reduction of blood flow starting from the time of its maximal plasma concentration. Raubasine alone does not induce any change in blood flow, while the combination of the 2 drugs significantly increases the blood supply to the affected limb. These favorable results, probably related to the ability of raubasine to induce a reverse vascular steal, suggest that the combination of this drug with a vasodilator such as papaverine may represent a new approach in the treatment of peripheral arterial insufficiency.

Protective role of collaterals in patients with coronary artery occlusion

We reviewed the clinical, hemodynamic and angiographic data of 105 patients with right coronary artery occlusion and 82 patients with left anterior descending coronary artery occlusion, subdivided into 3 groups by the presence and quality of collaterals to the occluded coronary (absent, poor or good collaterals). We found that patients with right coronary artery occlusion and good collaterals had a lower frequency of diaphragmatic myocardial infarction (60%) than patients with absent collaterals (100%) (P less than 0.01). In addition, in patients with old diaphragmatic myocardial infarction, both poor and good collaterals were associated with a lower frequency of severe asynergy of the diaphragmatic left ventricular segments at left ventriculography (54% and 14%, respectively), compared to patients with no collaterals to the right coronary artery (92%, P less than 0.02 vs. poor collaterals, P less than 0.001 vs. good collaterals). In contrast, in patients with left anterior descending coronary artery occlusion, the presence of either poor or good collaterals to the left anterior descending coronary artery was not associated with a lower frequency of old anterior myocardial infarction, or, in patients with old anterior myocardial infarction, with a less severe asynergy of the anterior left ventricular segments. Our results suggest that collaterals are effective in protecting the diaphragmatic left ventricular wall in patients with right coronary artery occlusion, but not the anterior left ventricular wall in patients with left anterior descending coronary artery occlusion.

Cardiovascular effects of histamine infusion in man

Histamine (H) is stored in man in the cardiovascular as well as in other systems, from where it can be released under exposure to immunologic and nonimmunologic stimuli. To understand better the hemodynamic changes produced in man by endogenous H release, we infused H for 3.5-7 min at the rate of 0.4 microgram/kg/min i.v. in four patients with normal left ventricular (LV) function undergoing diagnostic cardiac catheterization. We observed a significant fall in systolic, diastolic, and mean aortic pressure, systemic vascular resistance, LV end-diastolic pressure, and stroke index, and a significant rise in heart rate, cardiac output, and LV dP/dtmax, with small changes in mean pulmonary arterial pressure and pulmonary vascular resistance. During infusion there was also a significant rise in plasma H, epinephrine, and norepinephrine. All hemodynamic changes started 1-2 min after the beginning of H infusion and reverted to normal within 5 min from the end of the infusion. Subjective complaints were mild and transient in all patients. One patient progressed from first- to third-degree atrioventricular block, with prompt recovery of 1:1 atrioventricular conduction at the end of infusion. Thus, exogenous H administration in man at the rate of 0.4 microgram/kg/min produces significant and transient hemodynamic changes, mainly represented by systemic hypotension, tachycardia, and increased LV performance. These latter can be attributed to the associated increase in sympathoadrenergic activity, although a direct cardiac effect of H cannot be excluded.

Response of the left ventricular connective tissue to hypoxia

The collagen content (measured as myocardial concentration of hydroxyproline) and dry weight (expressed as ventricle weight to body weight ratio) were determined in the left ventricle of male Sprague-Dawley rats (200--220 g b.wt.) exposed to a simulated altitude of 7,000 m for 18 h a day for 10 days in a hypobaric chamber. Hypoxia resulted in a significant increase (P less than 0.001) in the mass of the left ventricle with a concomitant significantly increased collagen concentration (P less than 0.001). The data indicate that hypoxia effects the synthesis of a significant amount of connective tissue in the left ventricle, which is the ventricle not exposed to pressure load. These results may be related to clinical, hemodynamic, and pathologic observations showing the left ventricular dysfunction in patients with chronic respiratory insufficiency. Since the amount of collagen in the left ventricle might interfere with contractile function, it is suggested that the hypoxia in these patients could affect the left ventricular myocardium via a direct action on the connective metabolism.

Intropic effects of several antiarrhythmic drugs

The effects of intravenous administration of several quinidine-like antiarrhythmic drugs (bunaftine, monochloroacetyl ajmaline, lidocaine, mexiletine, disopyramide, aprindine, diphenylhydantoin, procainamide) on left ventricular performance, evaluated by systolic time intervals (STI), were studied in 100 patients with atherosclerotic heart disease. The STI were measured: the pre-ejection period (PEP), the isometric contraction time (ICT), the left ventricular ejection time (LVET), corrected LVET (LVETc), and the PEP/LVET ratio. The degree of impairment of left ventricular performance was maximal after aprindine and disopyramide administration. This was demonstrated by significant increases in the PEP, ICT, and PEP/LVET and by significant decreases in LVET and LVETc, in patients in both III-IV and I-II NYHA classes. Bunaftine, monochloroacetyl ajmaline, and lidocaine induced a less marked impairment of myocardial performance, since the PEP, ICT, and PEP/LVET increases were not significant compared to controls in patients in NYHA class I-II, and since no variation of LVET and LVETc were observed. Mexiletine effects on myocardial performance appear to be intermediate between these groups of drugs. Diphenylhydantoin and procainamide, considered separately because of their effects on heart rate and blood pressure which are not possessed by the other drugs, induced significant increases of PEP in NYHA class III-IV patients. However, the effects of these 2 drugs on myocardial performance may have been underestimated, due to the concomitant hemodynamic effect of these drugs.

Two-dimensional echocardiography in idiopathic enlargement of the right atrium. Reliability and limitations

A 36-year-old woman was admitted to our hospital with exertional dyspnea, palpitation and cardiac enlargement on standard chest X-ray. Physical examination did not reveal any significant abnormality and routine laboratory tests were normal. ECG showed atrial fibrillation and negative T waves in lead III and a VF, with a stiffened ST segment. M-mode echocardiography showed absence of pericardial effusion and normal size of both ventricular chambers. Two-dimensional echocardiography showed a large saccular dilation of the right atrium without significant enlargement of other cardiac chambers. A slight displacement of tricuspid valve leaflets was also present. Cardiac catheterization was effective in the diagnosis of idiopathic enlargement of the right atrium. Although two-dimensional echocardiography has some limitations in the diagnosis of this unusual malformation, it may prove useful in the noninvasive follow-up of these patients, in order to monitor the eventual increase of atrial size and to promptly detect late complications.

Dilazep-induced reduction of ischemic necrosis in rats with coronary artery occlusion

To assess whether dilazep reduces myocardial necrosis we assigned 72 rats that survived coronary artery occlusion to 3 groups. The first control group (n = 26) received coronary occlusion and was untreated. The second group (n = 21) received coronary occlusion and was treated with dilazep (150 micrograms/kg s.c.) every 8 hours for 48 hours. The third group (n = 25) was sham-operated. Forty-eight hours later the creatine-kinase activity of the left ventricle was measured. The calculated left ventricular fraction that survived the occlusion was larger in dilazep-treated rats (44.5 +/- 4.1% of left ventricle) than in controls (31.2 +/- 3.2%; P less than 0.05). Twenty-six more rats also underwent coronary occlusion; 12 were controls and the remaining 14 were treated with dilazep at the same time and dose as before and killed 21 days after occlusion. Infarct size was evaluated on histological sections of the hearts by planimetry. The amount of left ventricle preserved from necrosis was larger in dilazep-treated rats, 82.1 +/- 0.9%, compared to controls 69.5 +/- 1.4% (P less than 0.05). Dilazep seems effective in preserving myocardial tissue from ischemic necrosis, and its beneficial effects are long-lasting, producing permanent reduction of infarct size.

Prajmalium bitartrate in chronic ventricular arrhythmias: comparison with disopyramide

24-h ECG recordings were used to assess the efficacy of prajmalium bitartrate (PB) in reducing the incidence and the severity of premature ventricular complexes (PVCs), and to compare its antiarrhythmic action with that of Disopyramide. 13 patients with frequent PVCs were distributed randomly into 2 groups. The first group of 7 patients received PB 80 mg/day for 4 days as their first treatment, and disopyramide 400 mg/day for a further 4 days as the second therapy. The succession of the drugs was reversed in the other group of 6 patients. Analysis of the Holter recordings showed that PB and disopyramide reduced PVC frequency to a similar extent as compared to the corresponding wash-out period, viz. by 56.7% (p less than 0.05) and 62.1% (p less than 0.01), respectively. Thus, PB appears to be an effective antiarrhythmic drug and comparable to disopyramide. It may be used to prevent premature ventricular complexes and runs of ventricular tachycardia.

Bilateral ventricular hypertrophy in rats exposed to acute or chronic hypobaric hypoxia

Development of bilateral ventricular hypertrophy in animals exposed to sustained hypoxia is demonstrated. Female Sprague-Dawley rats (180-200 g) were subjected to acute (0.40 atm/24 h) or chronic intermittent (0.40 atm/18 h/day/7days) hypobaric hypoxia. Control animals were maintained at room pressure. The changes in ventricular mass (right ventricle and left ventricle including the septum) were evaluated on the basis of the dry weight values immediately at the end of hypoxic stimulus. Data show that both acute and chronic hypobaric hypoxia allow rate to develop a significantly degree of hypertrophy in the left as well as in the right ventricle. The factors involved in the genesis of the left ventricular hypertrophy in hypoxic conditions are presented.

Systolic time-interval evaluation by thermistor plethysmography during uninterrupted dynamic stress test in normals and in patients with coronary artery disease

18 patients with coronary artery disease (CAD) and 21 normal subjects underwent a triangular bicycle exercise test. Systolic time intervals (STI) were calculated at rest and every 2 min during exercise. Under resting conditions, STI were similar in the two groups. During exercise, the ejection time index (ETI), i.e. left ventricular ejection time (LVET) corrected for HR, rose significantly more in CAD patients, as compared to normals. Pre-ejection period (PEP) was also differently affected by exercise in CAD patients, who showed a more shortened PEP (p less than 0.001) in the early stage of dynamic stress. PEP/LVET ratio, which in the control group decreased continuously, in CAD patients fell during exercise at lower work loads (p less than 0.001), whilst rose during strenuous exercise. Finally, significant differences (p less than 0.001) were found in the percent change (% delta) PEP/LVET ratio between the two groups during the early phase of exercise, in which no superimposition of single values was present. Therefore, this last parameter seems the most reliable to differentiate clearly CAD patients from normal subjects, but its use must be limited at early exercise.

Quantitative assessment of infarct size in isoproterenol-infarcted rats

The authors performed a number of experiments aiming at quantifying the infarct size in Sprague-Dawley male rats. The experimental model employed was isoproterenol (ISP) induced, infarctlike myocardial lesions. In quantifying the extent of the infarct area they compared the cross reliability of enzymatic and histological methods. ISP was administered in two subcutaneous injections (50 mg/100 Gm body weight) at a 24 hour interval. At the peak of the necrotic process (48 hrs after the first injection), the heart was subjected to enzymatic or histological studies. Thus, a group of infarcted animals (n = 25) and their controls (n = 15) underwent the assessment of creatine kinase (CK) content in the homogenate of the myocardium. Another group of animals (n = 15) was used for histological observations, including measurement of infarct size by planimetry from histological sections. A good relationship was observed between the percentage of necrotic tissue calculated on the basis of CK values (69.11 +/- 2.39%) and the infarction area assessed by planimetry (72.37 +/- 2.69%) (mean +/- standard error of the mean [SEM]). Thus, the present study confirms that ISP-induced myocardial lesions are a simple and reliable model for experimental infarct. Moreover, the assessment of the CK content in the heart is correlated with histological studies by planimetry, and is suggested as a direct enzymatic method to quantify the extent of myocardial necrosis.

Further observations on the electrophysiologic effects of oral amiodarone therapy

A case is presented of a reversible intra-Hisian block occurring under amiodarone treatment for atrial tachycardia in a patient without clear intraventricular conduction abnormalities. His bundle recordings showed an atrial tachycardia with intermittent exit block and greatly prolonged BH and HV intervals (40 and 100 msec, respectively). Thirty days after amiodarone discontinuation, His bundle electrograms showed atrial flutter without intra-Hisian or infra-Hisian delay. Amiodarone should be used with caution during long-term oral therapy in patients with or without clear intraventricular conduction defects.

Propranolol-induced reverse vascular steal in arteriopathic patients

The vascular steal phenomenon, i.e., the shunting of blood from ischemic to normally perfused areas, has been described in the affected limbs of arteriopathic patients after taking vasodilating drugs. This study was per formed to ascertain whether the reverse situation can be induced, i.e., whether vasoconstriction of the vessels supplying the nonischemic zone could increase the amount of blood reaching the ischemic area. Accordingly, 49 arteriopathic subjects were selected on the basis of the plethysmographic evidence of a reduction of blood flow in the affected limb following an IV injection of xanthinol-nicotinate. In a first group of 10 patients, the reduction of blood supply to the affected limb induced by xanthinol-nicotinate was inhibited when this drug was administered in combination with 5 mg of propranolol. In another 22 patients, the plethysmographic response observed after xanthinol-nicotinate alone was reversed when this drug was injected after 10 mg of propranolol. Actually, the blood perfusion to the affected limb rose significantly at all times of recording as compared to basal values. Finally, in a third group of 10 patients in whom xanthinol-nicotinate induced a significant reduction of blood flow, propranolol did not modify it. The angiographic studies performed in 3 patients confirm the plethysmographic results. Xanthinol-nicotinate alone induces a reduction of the vascular filling in the affected limb, while the combination of the vasodilating drug with 10 mg of propranolol is able to improve the vascular filling in the affected area. These results indicate that the overwhelming action of α-adrenoceptors obtained in the normal area by the β-receptors' blockade favors a beneficial redistribution of blood flow which might be considered a reverse vascular steal.

Effects of combined alpha- and beta-blockade by labetalol in patients with coronary artery disease

1 The effect of labetalol 100 mg orally twice daily on exercise tolerance has been compared with placebo in 19 normotensive subjects with angiographic evidence of coronary artery disease. 2 Labetalol, at the same work load as during placebo exercise, significantly reduced systolic and diastolic blood pressures, as well as heart rate and rate-pressure product. 3 Similarly, ST segment depression was reduced by labetalol from 2.0 +/- 0.4 to 1.36 +/- 0.6 mm (P less than 0.001), thus enabling an increase in exercise tolerance from a control value of 83.7 +/- 18 to 95.3 +/- 19 W (P less than 0.005). 4 In seven other patients, also with coronary artery disease, the haemodynamic effects of a single 0.6 mg/kg intravenous dose of the drug was evaluated during exercise. 5 Compared with conditions during control exercise, labetalol induced a significant reduction in rate-pressure product from 17228 +/- 2375 to 13445 +/- 2404 mmHg/min (P less than 0.005) and in peripheral vascular resistance from 612.0 +/- 61.2 to 512.7 +/- 36.2 dyn cm-5 m-2 (P less than 0.0025). These events were not accompanied by any change in cardiac index and in dP/dT left ventricular end-diastolic pressure (LVEDP) ratio. 6 These data suggest that labetalol may induce reduction in myocardial oxygen consumption, thereby increasing exercise tolerance in patients with coronary artery disease, without impairment of left ventricular performance.

The reflex control of arginine-vasopressin release in essential hypertension

1. The reflex control of arginine-vasopressin release was studied in 12 essential established hypertensive patients and in 12 age-matched normal subjects by comparing the effects of head-up tilt and a variable-pressure neck-chamber. 2. After 45 min 85 degrees head-up tilt, normal subjects showed an increase in plasma arginine-vasopressin and in plasma renin activity, while plasma volume decreased. In hypertensive patients, plasma arginine-vasopressin showed changes after tilt opposite to those of controls, while the changes in plasma renin activity and plasma volume were similar to those observed in the normal group. In both groups the changes in systolic and diastolic blood pressure were not statistically significant. A reduction in carotid sinus transmural pressure obtained by increasing neck-tissue pressure (+50 mmHg) by means of a neck-chamber, evoked different responses in mean blood pressure in the two groups, but failed to induce any significant change in plasma arginine-vasopressin concentration both in the normal and in the hypertensive subjects. 3. These results seem to suggest that carotid sinus baroreceptors, though active in blood pressure control, do not play a direct role in arginine-vasopressin release and, therefore, the opposite response of arginine-vasopressin observed after tilt in the two groups of subjects should be ascribed to more complex mechanisms.

Severity of mitral regurgitation assessed by echocardiography. Reliability and limitations

To assess whether echocardiography may represent a useful mean to evaluate the degree mitral regurgitation (DR), left ventricular diastolic internal dimension (LVIDd), left atrial dimension (LAD), and velocity of circumferential fiber shortening (Vcf) were compared to DR assessed by left ventriculography in 48 patients with primary (n = 21) and cardiomyopathic (n = 27) valvular incompetence. In patients with good left ventricular contractility, i.e. with Vcf values above 1.02, a significant positive linear correlation was found between LVIDd and DR (LVIDd = 5.38 + 0.45DR; r = 0.72; p less than 0.001). In contrast, in patients with depressed left ventricular function, i.e. with Vcf values below 1.02, LVIDd did not correlate to DR. In either group LAD and Vcf did not correlate to DR. Thus, echocardiography may provide useful semiquantitative information concerning DR only in patients with preserved left ventricular performance.

Non-invasive evaluation by thermistor plethysmography of left ventricular performance during dynamic exercise. Comparison with echocardiography

The purpose of this study was to evaluate the reliability of two non-invasive techniques (STI and echocardiography) in assessing cardiovascular response during exercise. STI were obtained using a new carotid pulse transducer (thermistor pulse) proved to be reliable in exercise recording. The study population included 12 male rowers (age 15-20 years), who performed supine bicycle exercise; STI and echocardiographic recording of left ventricle were simultaneously obtained at rest and continuously throughout the exercise period. A negative linear correlation (r=-0.782; p less than 0.001) was found between PEP (pre-ejection period) and %LVID (fractional shortening of left ventricle), reliable indexes of cardiac contractility measured by the two techniques. A lower, but significant correlation (r=0.643; p less than 0.001) was present between ETI (left ventricular ejection time corrected by heart rate) and SV (stroke volume) indexes of pump function. The present study shows that STI measured with this new technique, can be employed in evaluating left ventricular function in those patients in whom a good echocardiogram is difficult to record during exercise.

His bundle electrogram recording using a multipolar electrode catheter via the arm veins

In eighteen patients with atrioventricular conduction disturbance, His bundle electrograms were studied via the arm vein. A 6F Berkovits-Castellanos USCI hexapolar electrode catheter was introduced into the right atrium and looped across the tricuspid valve in a "golf club" shape. The main aim was to leave the two distal electrodes in contact with the atrial endocardium to perform atrial pacing, while displaying the other four electrodes along the superior angle of the tricuspid valve for proximal and distal His bundle recordings. His bundle electrograms were successfully obtained in all cases. The arm approach provides an alternate route whenever the femoral approach is not feasible. Moreover, the use of an hexapolar electrode catheter provides some practical advantages: 1) it enables atrial pacing to be performed, as well as proximal and distal His bundle recording to be obtained, by using the same multipolar electrode catheter; and 2) it allows long-term monitoring of His bundle potentials, in view of the stability of His bundle recordings. Finally, the arm approach could be the method of choice for the study of His bundle electrograms during leg supine exercise in selected patients.

Inhibition of hypoxia-induced cardiac hypertrophy by verapamil in rats

Male Sprague-Dawley rats (200-220 g) were employed to study the effect of a calcium antagonistic drug on hypoxia-induced myocardial hypertrophy. The hypoxic condition was obtained by exposure of animals to reduced barometric pressure in a hypobaric chamber. The rats, divided in groups, were exposed to acute or chronic intermittent hypoxia (0.42 atmospheres of air for 24 hrs or 0.42 atm for 12 hrs per day for 10 days, respectively). Verapamil (VRP) was given subcutaneously in a total dose of 200 mg/kg/b.w./rat. In hypoxic rats, the drug significantly reduced the values of dry heart weight calculated on the basis of its relationship to total body weight. This phenomenon is probably due to: (1) reduced activation of the contractile system and a thereby resulting decrease in ATP breakdown as a result of blocking of Ca++ inflow into myocardial cells; (2) the effect of Verapamil on hypoxia-induced pulmonary hypertension and/or (3) a direct effect of the drug on the myocardial cell.

Relationship between systolic time intervals and heart rate during atrial or ventricular pacing in normal subjects

Systolic time intervals (STI) are regarded as good indices of cardiac performance in many heart diseases. It must be considered, however, that they are temporally related to the cardiac contraction cycle and, therefore, may be modified by heart rate changes. Thus, it is necessary to define the possible relationship between STI and heart rate changes. In this study, changes in heart rate were induced by atrial and ventricular pacing. Tachycardia caused a proportional decrease of left ventricular ejection time (LVET) (y=275.142-1.0025 x, r=0.76, p less than 0.001 for atrial pacing and y=298.28-0.691 x, r=-0.75, p less than 0.001 for ventricular pacing, respectively), but did not modify the pre-ejection period (PEP) and the isometric contraction time (ICT) and the electromechanical interval (QS1). These results demonstrate that while LVET must be corrected for the changes in heart rate, no correction of PEP and ICT is necessary.

Myocardial hypertrophy in the rat. Correlation between two experimental models

Two different conditions responsible for cardiac hypertrophy in the rat were investigated: the first one is isoproterenol-induced myocardial infarct, the second is exposure to hypoxia (0.42 atmospheres/24 h) in hypobaric chamber. To demonstrate that in both experimental models stimulation of protein synthesis is an absolute requirement to induce cardiac hypertrophy, a variety of techniques were employed including: evaluation of dry heart weight value, concentration of radiothallium (201T1) in the heart and effects of inhibitors of protein synthesis (Puromycin). Experimental results have showed: (A) a significant increase (p<0.001 as compared to control group) of dry heart weight values both in isoproterenol-treated and hypoxic rats; (B) a significant increase over control group (p<0.001) in myocardial 201T1 concentration in isoproterenol-treated rats; (C) total inhibition of cardiac hypertrophy in Puromycin treated group subjected to hypoxia. Finally, on the basis of different mortality observed in infarcted (85.0%) or hypoxic (5.0%) rats treated with Puromycin (40 mg/Kg body weight i.p.) a different role of cardiac hypertrophy in 2 experimental conditions is postulated: in the case of infarct-like lesions the cardiac hypertrophy has compensatory significance; under hypoxic stimulus is only due to increased cardiac work.