The effects of atropine on sinoatrial conduction time directly measured from sinus node electrogram. A comparison with results furnished by indirect methods

The effects of atropine on sinoatrial conduction time (SACT) measured directly (SACTD) from the sinus node electrogram (SNE) were investigated in 15 patients with normal sinus node function. A comparison was undertaken with the results furnished by indirect methods which employ premature (SACTS) and asynchronous atrial stimulation (SACTN) to calculate SACT. In the control state SACTD was 92.5 +/- 16.4 ms, SACTS 78.2 +/- 22 ms, and SACTN 97.9 +/- 32.2 ms. After atropine SACTD was 70.6 +/- 15.6 ms (P less than 0.0005), SACTS 46.7 +/- 14.3 ms (P less than 0.0005) and SACTN 43.1 +/- 12.7 ms (P less than 0.0005). Mean percent decreases of SACTN (51.6 +/- 21) and SACTS (37.4 +/- 18) were statistically greater than that of SACTD (23.5 +/- 13.3) (P less than 0.0005 and P less than 0.01 respectively). While the reduction of SACTS and SACTN was greater than that of sinus cycle length (SCL) (29.2%), SACTD showed a reduction significantly less than that of SCL (P less than 0.005). Thus, SNE recording confirms that atropine induces a shortening of SACT in normal patients, but significantly less than that indicated by indirect methods.

Short-term responses to cardiac rehabilitation after acute myocardial infarction. Cardiac function evaluation before and after physical training at rest and during stress test

Whether physical training, soon after myocardial infarction (MI), has effects upon intrinsic cardiac function at rest and during exertion remains unresolved. We have evaluated ventricular function using radionuclide angiography at rest and during stress testing before and after 3 months' physical training. This has been correlated with the site of MI and with changes in the ST segment during the maximal exercise test performed before the postmyocardial infarction rehabilitation program. We have studied 27 patients, mean age 54 +/- 10 years, in NYHA class I or II. Twelve showed no changes in the ST segment during erogmetric stress test (group 1); seven showed ST segment depression greater than 1 mm in leads different from those of MI (group 2); eight showed ST segment elevation of 2 mm (group 3). Twelve patients had had anterior MI only (AMI group); twelve inferior MI only (IMI group). After rehabilitation, all patients showed an increased work capacity and a decreased double product at the same work load. In the total group, significant increases were found in the left ventricular ejection fraction (LVEF) and in the contractile regional performance (LVwm) at rest, as well as a lesser decrease in the LVEF during handgrip test. Group 1 showed a significant increase in LVEF, associated with a decrease in left ventricular end-diastolic volume (EDV) at rest. Group 2 showed unchanged variables after rehabilitation. Group 3 showed a better LVEF during handgrip with an increase of EDV at rest. The AMI group showed a better LVEF and LVwm at rest and a better LVEF during handgrip. IMI group showed a better right ventricular ejection fraction during handgrip without improvement in LVEF. No patient with IMI had septal asynergy. We conclude that the effects of rehabilitation were linked to the site of MI and to the functional dynamic status of both ventricles.

An unusual PR interval alternans during 2:1 atrio-ventricular block

In a case of a 2:1 second degree A-V block during sinus rhythm, PR intervals of two different durations occur, either separately or alternating beat-by-beat. The longer intervals are not caused by concealed conduction in the A-V junction of the preceding blocked impulses and the shorter ones are not due to supernormal conduction induced by the blocked impulses. This primary PR interval alternans is alternating from a pathophysiological point of view; it only concerns every other impulse alternately traveling along the faster and slower A-V junctional pathway.

Systemic hemodynamics and renal function in cirrhotic patients during plasma volume expansion

Systemic hemodynamic impairment (hepatocirculatory failure) has been suggested as one of the possible factors which may explain the renal hemodynamic alterations found in the late stage of liver cirrhosis, typical of the hepatorenal syndrome. 20 patients, divided into two groups of 10 sodium retainers and 10 sodium excretors, affected by liver cirrhosis with portal hypertension and ascites, were studied. Renal functional parameters (diuresis, urinary and plasma electrolytes, urine to plasma osmolality and creatinine ratios and creatinine clearance) were evaluated before and after acute volume expansion with 1,000 ml of 10% dextran in saline, infused through a catheter located in the right atrium. Hemodynamic tests (cardiac index, systemic vascular resistance, right atrial pressure and capillary wedge pressure) were performed before, during and after expansion. Cardiac index decreased in 6 patients (sodium excretors) after a 500-ml infusion and rose again after 1,000 ml in 5 of them. The remaining 14 patients showed a progressive and significant increase of cardiac index. A strong inverse relationship between cardiac index and systemic vascular resistance was observed (r = -0.87; p less than 0.001). The mean left-ventricular function curve showed a slow response in most sodium excretors and a normal response in the sodium-retaining group, without significant difference between the two groups. Sodium excretion significantly improved after expansion in both groups of patients. No relationship was found between hemodynamic response and renal function. These data show that cardiocirculatory function is normal, even in sodium-retaining cirrhotics.

Echocardiographic evidence of increased mitral-aortic separation in discrete subaortic stenosis

The present study reports the two-dimensional echocardiographic pattern of 6 patients affected by discrete subaortic stenosis. The diagnosis was proven at cardiac catheterization. The echocardiographic picture was characterized by a deformity of the left ventricular outflow tract due to an inward-protruding upper septum and to an elongated and domed mitral-aortic separation. The latter finding has been described in anatomic studies but has never been reported with wide-angle echocardiography.

Regional left ventricular wall motion abnormalities in chronic volume overload

Computer-assisted analysis of left ventricular (LV) wall motion has been performed in 12 patients (pts) with chronic volume overload and in seven normal subjects. All pts were in sinus rhythm, without congestive heart failure and without coronary artery disease at selective coronary angiography; 30 degrees right anterior oblique ventriculograms were employed in each case. Thirty-six radiants were automatically traced and the percent shortening of each radiant was calculated using two different reference methods (fix and floating methods). In valvular heart disease (VHD) pts LV volumes were significantly increased, and ejection fraction and LV eccentricity were significantly reduced. LV eccentricity inversely correlated with LV volumes. VHD pts showed regional LV abnormalities. Inferoapical and anterior wall motion was significantly reduced (two-sample t-test P less than 0.05) using the fix method. With this method a significant inverse correlation between percent shortening of the radiants correspondent to the inferoapical region and end-diastolic and end-systolic volumes was found; a significant direct correlation was found with LV systolic eccentricity. Ejection fraction directly correlated with the percent shortening of radiants correspondent to both the anterior and inferior regions. The role of LV "dynamic geometry" alterations as a possible cause for the observed regional LV wall motion abnormalities is emphasized.

[Evaluation of sinoatrial conduction time by recording the sinus node potential. Comparison with indirect methods of evaluation]

A method of recording the sinus node potential (SNP) has recently been introduced in clinical electrophysiology. The sinoatrial conduction time can now be measured directly (SACTD) as the interval between the onset of the SNP and the onset of atrial activation. We measured the SACTD in 16 normal subjects and in 7 patients with sinus node dysfunction. These values were compared with those obtained by the indirect methods of Strauss et al (SACTS) and Narula et al (SACTN). In normal subjects the SACTD ranged from 50 to 130 ms (average 84,4 +/- 22,35); the SACTS, from 55 to 160 ms (92,9 +/- 29,3), and the SACTN from 70 to 175 ms (113,2 +/- 28,8). In patients with sinus node dysfunction the SACTD ranged from 200 to 290 ms (227 +/- 32,5), the SACTS, from 52 to 198 ms (111,8 +/- 59,3) and the SACTN from 89 to 251 ms (142,3 +/- 63). No significant difference was observed between normal and pathological subjects using the indirect methods of evaluation. However, the SACTD method showed a very significant difference between the two groups (p less than 0,0005) with no overlap. No correlations were observed between the values obtained by the indirect and direct methods of measuring SACT.

Effect of dextran infusion on left atrial size in normal subjects

The purpose of this study was to evaluate left atrium dimension during acute volume loading. Low molecular weight dextran solution (1,000 ml) was continuously infused in 10 subjects without cardiac disease. Measurements of pulmonary arterial, capillary wedge, right atrial and systemic blood pressures, cardiac output, heart rate and M-mode left atrial maximum diameter were made in basal conditions and after 250, 500, 750 and 1,000 ml of dextran. In 4 subjects a two-dimensional echocardiogram was also obtained in the short axis and four-chamber views. Dextran produced the following changes (mean values +/- standard deviation) in haemodynamic variables: right atrial and wedge pressures increased from 3.2 +/- 1.55 to 12.3 +/- 3.08 mm Hg (p less than 0.001) and from 6.9 +/- 1.45 to 20.6 +/- 3.44 mm Hg (p less than 0.001), respectively. Stroke volume increased from 70.5 +/- 31.6 to 86.6 +/- 24.6 ml/beat (p less than 0.05). Heart rate increased from 81.0 +/- 15.8 to 95.0 +/- 12.3 beats/min (p less than 0.05). Left atrial maximum diameter showed a slight increase after 500 ml of dextran (from 39.5 +/- 4.1 to 43.6 +/- 5.0 mm, p less than 0.05). It did not further increase by continuing the infusion up to 1,000 ml despite the marked increase in wedge pressure. The results show that left atrial size is partly independent of haemodynamic changes and that the compliance of the left atrium is relatively low. This finding is consistent with the common clinical observation that the left atrium is only slightly enlarged in acute mitral insufficiency.

Hemodynamic pattern following K-strophanthin in normal and coronary artery disease patients

Hemodynamic effects of K-strophanthin (0.005 mg/kg i.v.) were evaluated in 7 normal and in 13 non-failing coronary artery disease patients (CAD). Volumetric parameters were obtained by single plane left ventricular angiography. The indexes of "pump" function, the end-systolic pressure-volume relationship and the ratio of peak pressure to systolic volume were also evaluated. Heart rate was maintained constant by atrial pacing. In normal subjects K-strophanthin exerted small effects without peripheral vasoconstriction. CAD patients showed different response to K-strophanthin in vascular tone: an increase (Group 1) or a decrease (Group 2) in total systemic resistance (TSR). No significant differences were found in basal values between the two CAD groups. In Group 2 the indexes of "pump" function increased after K-strophanthin and the end-systolic pressure-volume points shifted upward and to the left, while in Group 1 no improvement in cardiac function was observed and the end-systolic pressure-volume points shifted upward and to the right. Furthermore, we found a direct significant correlation between the percent changes of TSR and end-systolic volume index, and a negative significant correlation between the percent changes of TSR and stroke volume index. Our results show that K-strophanthin in CAD non-failing patients can have either a positive effect or a lack of improvement in ventricular performance. These effects correlate with changes in total systemic resistance.

Pulsed Doppler echocardiography for diagnosis of ventricular septal defects

In order to assess the performance of pulsed Doppler echocardiography and to examine the factors affecting its reliability for the diagnosis of ventricular septal defects, 51 patients, in whom angiographic studies had recently been performed, were investigated before and after operation by this technique. The diagnosis was correct in all cases with left-to-right shunt, when the defect was located either in the upper muscular or in the infracristal portion of the septum, even when pulmonary hypertension or additional cardiac malformations were present. Pulsed Doppler echocardiography did not differentiate between supracristal ventricular septal defects and obstruction of the right ventricular outflow. Apical muscular defects were never observed in our cases. Defects of the inlet portion were not localised by the method. In cases with bidirectional shunt, pulsed Doppler echocardiography failed to provide any diagnostic clue. When a right-to-left shunt was present, only in one case with membranous pseudoaneurysm could pulsed Doppler echocardiography provide an exact description of the haemodynamics before and after operation. In 12 of 22 patients with tetralogy of Fallot, pulsed Doppler echocardiography showed flow tracings possibly related to the septal defect. The site of defect and the extent and direction of intracardiac shunting seem to be the main factors affecting its diagnostic performance in ventricular septal defects.

Effect of isoproterenol on the "early repolarization" syndrome

A study has been carried out on a group of subjects with RS-T segment elevation, a normal variant of early repolarization. Following isoproterenol administration, the RS-T segment became isoelectric. In most cases this was accompanied by shorter QT and longer QTc intervals. The same effects were observed after physical exertion but not after atropine or amyl-nitrite. Propranolol administration exaggerated RS-T elevation. Considering the mechanism with which isoproterenol acts and some analogies with the electrocardiographic picture experimentally obtained by means of the unilateral stimulation of the stellate ganglions, the hypothesis is advanced that the normal variant of early repolarization is related to an enhanced activity of the right sympathetic nerves.

[Dynamic geometry of the left ventricle. Relaxation and elasticity indices]

A study was made of 34 patients with valve defects or arterial hypertension and a haemodynamic picture of left ventricle pressure or volume load. Echocardiography and haemodynamic investigated-established the size and mass of the left ventricle and also enabled its indices of contractility, relaxation and distensibility to be determined. The series was divided in accordance with the dynamic geometry of the left ventricle. In concentric hypertrophy, telediastolic rigidity increased in proportion to ventricular thickness and mass. In eccentric forms and ventricular dilatation, diastolic distensibility was reduced in cases with a high filling pressure. The relaxation values bore no relationship to distensibility and telediastolic compliance. The relaxation rate in protodiastole diminishes in proportion to functional depression of the left ventricle.

[The Doppler-echocardiography in the study of transvalvular pulmonary flow (author's transl)]

The AA. studied 96 subjects: 74 normals, 15 patients with pulmonary stenosis, 6 with pulmonary regurgitation and 1 with combined stenosis and pulmonary regurgitation, by using pulsed Doppler echocardiography. This technique, which supplements M-mode echocardiography with Doppler flow detection, allowed determination of direction and quality--laminar or turbolent--of flow through pulmonary valve. In our experience, pulsed Doppler echocardiography is a sensitive and specific method for detection of pulmonary stenosis and regurgitation and extends ultrasound diagnosis beyond the capabilities of M-mode echocardiography.