Detection of coronary artery disease in the presence of left ventricular atrophy

To evaluate the accuracy of exercise echocardiography for the recognition of coronary artery disease in the presence of left ventricular hypertrophy 70 patients were studied. Significant coronary artery disease was present in 25 patients and left ventricular hypertrophy had 29 patients. All patients underwent an exercise ECG and echocardiographic test during which cine-loop digitized echocardiography was obtained. Wall motion was analyzed and a regional wall motion score index was calculated. The overall sensitivities of exercise ECG and echocardiography for detecting coronary artery disease were 60% and 64%, respectively, and the specificities were 49% and 78%, respectively. In patients with left ventricular hypertrophy the specificity of exercise echocardiography was higher (71%) compared to exercise ECG (21%) while in patients without hypertrophy the sensitivity was higher (70% vs. 40%, respectively). Of the 19 patients with a non-diagnostic stress ECG, echocardiography correctly identified 100% of those with coronary artery disease but only 53% of those without disease. It is concluded that exercise digital echocardiography represents a good diagnostic alternative to the exercise ECG for identifying coronary artery disease in the presence of left ventricular hypertrophy and should be useful in patients with a non-diagnostic exercise ECG.

Atrial pressure and experimental atrial fibrillation

A possible profibrillatory effect on the atria of an elevated atrial pressure and the site of atrial stimulation was examined. In 15 anesthetized dogs, right or left atrial or biatrial pacing was applied at a high rate (300-600/min) for 5 seconds at double threshold intensity under a wide range of atrial pressures achieved by venous or arterial transfusion or bleeding. Induction of atrial fibrillation in 236 of 1,971 pacing runs was associated with a significantly higher (P < 0.001) atrial pressure (21.6 +/- 12.2 mmHg, mean +/- SD) than maintenance of sinus rhythm (16.8 +/- 11.1 mmHg in 1,735 of 1,971 pacing runs). Stimulation of the right atrium resulted in atrial fibrillation more frequently than left atrial or biatrial stimulation, with biatrial stimulation less frequent than right or left atrial stimulation. The induction of atrial fibrillation was related to the atrial pressure and to the site of stimulation but not to the pacing rate or the prepacing heart rate. The prepacing heart rate, associated with failure to induce sustained atrial fibrillation, was higher than that associated with atrial fibrillation in 12 of 15 experiments (significantly in 6) and not significantly lower in 3 of 15. Atrial fibrillation lasting 1 minute or more was more frequently associated with simultaneous stimulation of both atria than of either atrium alone. Thus, an elevated atrial pressure may facilitate the induction of atrial fibrillation. The site of stimulation also plays an important role for both the induction and maintenance of atrial fibrillation in this model.

Effect of preload and afterload on ventricular arrhythmogenesis

To examine whether it is an increase in preload or afterload that may cause ventricular arrhythmias, the ventricles of 13 anesthetized open-chest dogs were bandaged. Next, metaraminol, an almost pure alpha stimulator, was given, followed by removal of the bandage. The ventricles were then sucked in a plastic cup, which was finally removed. The systolic and diastolic ventricular pressures were measured, and the presence of arrhythmias (ventricular ectopic beats or ventricular tachycardia) was observed. Banding the ventricles caused a significant diminution of systolic pressure (-42 +/- 38.0 mmHg; mean +/- SD) and a rise in diastolic pressure (+3.5 +/- 3.7), starting from control values of 126 +/- 36/6.5 +/- 3.0, but no arrhythmia. Metaraminol raised both pressures (+122 +/- 58 and +9.0 +/- 10.3) and caused ventricular arrhythmias in 6 of 13 experiments. Removing the bandage further increased the systolic pressure (+45 +/- 42) and reduced the diastolic pressure (-7.2 +/- 10.3), but made the arrhythmia worse in 10 of 13 experiments. Suction reduced both pressures (-166 +/- 96 and -5.4 +/- 14) and stopped all arrhythmias. Removing the cup increased both pressures (+133 +/- 68 and +15.5 +/- 15.3, respectively) and worsened the arrhythmia in seven of eight experiments. In general, deterioration of ventricular arrhythmias was observed in 23 of 25 maneuvers with either an increase or no change in systolic pressure, but in none of the maneuvers was there a decrease (P < .0001) in systolic pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Incidence and other epidemiological characteristics of sudden cardiac death in northwest Greece

Sudden cardiac death (SCD) has not been investigated separately in Greece. The aim of this study is to describe the epidemiological characteristics of people dying suddenly out of hospital in an area of Greece. In 1990, a population based study was started to detect the cases of people dying suddenly out of hospital (< 1 h after onset of acute symptoms or < 6 h after being seen alive) in a closed population in Northwest Greece (Ioannina area: 160,000 inhabitants). During a 3.5 year period, 283 potential cases aged 30-70 years were identified by monitoring the mortality in the emergency rooms of the two hospitals of the area, the coroner's office and the death certificates from the Government Department of Statistics. The diagnosis of SCD was established in 223 (183 men, 40 women; mean ages 59 and 61 years respectively) after visiting and interviewing the relatives and/or the family doctors within 12 days (range 1-28) after the death. SCD in the study accounts for 50% of all cardiovascular deaths and is the most common cause of death after neoplasia. The most common place of death was home (151 cases, 68%), and in 174 cases (78%) deaths occurred while the patients were relaxing or during routine activities. Prodromal symptoms were reported in 57 cases (26%). The time of day of death showed a circadian variation, with a peak in the late morning from 9:00 to 12:00. Ninety four (42%) had a prior history of heart disease. One hundred and ninety one cases (86%) occurred in the subgroup of age 50-70 years.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac involvement in collagen diseases

The purpose of this study is to evaluate the early morphological and functional abnormalities of the heart in patients with collagen disease. The study population was free of risk factors for coronary artery disease and without any clinically evident cardiac manifestations. In 62 patients with collagen disease (25 with progressive systemic sclerosis, 19 with systemic lupus erythematosus, 15 with rheumatoid arthritis, three with dermatomyositis) and in 40 healthy subjects an echocardiographic study was performed. Echocardiographic examination from the apical four-chamber view was performed at rest and during the end of a 3 min isometric exercise with handgrip. Global and regional ejection fraction of the left ventricle were calculated. In the group with progressive systemic sclerosis the left ventricular mass index was significantly higher than in the control group (110.78 +/- 48.61 vs 82.18 +/- 28.46 g.m-2) and the ejection fraction (53.61 +/- 7.95%) was the lowest of all groups (control: 61.47 +/- 8.52%, systemic lupus erythematosus: 59.04 +/- 8.58%, rheumatoid arthritis: 62.38 +/- 6.88%). Regional ejection fraction analysis revealed a major dysfunction of the proximal segment of the interventricular septum, in all groups. During isometric exercise, the global and regional ejection fraction did not change significantly, although differences between groups disappeared. In rheumatoid arthritis, mitral and aortic valve leaflet separation appeared to be reduced. In the group with systemic lupus erythematosus, mild abnormalities were noticed, although the mean age and duration of the disease were the smallest compared with the other groups. In conclusion, patients with progressive systemic sclerosis mainly present left ventricular hypertrophy with a reduced ejection fraction while rheumatoid arthritis patients show a predominant valve dysfunction.(ABSTRACT TRUNCATED AT 250 WORDS)

Some observations on the mechanism of pressure related atrial fibrillation

In order to investigate the effect of atrial pressure on the propensity of the atria to fibrillate and the mechanism of this association, the right atrial pressure was changed acutely by transfusion-bleeding in 12 anaesthetized open-chest dogs. Under various atrial pressures the conduction time was measured between two pairs of hook electrodes positioned on the two atrial appendages respectively. The effective refractory period was measured by continuous pacing of the right atrium at a 250 ms cycle length at double threshold intensity and interpolating a progressively earlier stimulus after each eighth paced beat. The propensity of fibrillation was studied by rapid (450 min-1) pacing of the atria at double threshold intensity for 10 s at different atrial pressures. At a high (> or = 14 mmHg) atrial pressure the conduction time (45.7 +/- 14.2 ms) was significantly (P < 0.01) longer, the effective refractory period (157.9 +/- 15.2 ms) significantly (P < 0.01) longer and the atrial fibrillation (11/19 or 57.9%) significantly (chi 2 = 9.95, P < 0.001) more common than at a low (< or = 10 mmHg) pressure (35.2 +/- 11.6, 146.2 +/- 12.4, 3/24 or 12.5%, respectively). Analysis of variance showed that the probability of atrial fibrillation was significantly affected by the atrial pressure but not by either the conduction time or the effective refractory period. The findings suggest that an increase in right atrial pressure by acute volume overload prolongs the inter-atrial conduction time and right atrial refractoriness and increases the propensity of the atria to fibrillate by rapid atrial stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of acute ventricular pressure changes on QRS duration

The effect of acute changes in ventricular pressure is examined on the QRS duration to clarify the mechanism of ventricular pressure-related arrhythmogenesis. Ventricular pressure was changed acutely by arterial transfusion-bleeding into an open-air ventricular pressure reservoir that was either off or on a metaraminol intravenous drip. While maintaining ventricular pressure at several levels, the QRS duration was measured at 200 mm/s paper speed. The QRS duration correlated significantly with the left ventricular pressure in all 14 dogs examined. An average change in ventricular by 100 mmHg was associated with a change of about 18% in the QRS duration. An acute ventricular pressure elevation impairs the ventricular conduction, which may contribute to ventricular pressure-related arrhythmogenicity.

High blood pressure and ventricular arrhythmias

Here we review the blood pressure-ventricular arrhythmia relationship. An increase in blood pressure, by any means, may induce ventricular arrhythmias both experimentally and in patients with a history of ventricular ectopic beats. Conversely, a decrease in blood pressure may eliminate ventricular arrhythmias due to other causes. The increased pressure is sensed in the ventricles. Both systolic and diastolic loading may induce important electrophysiological changes. However, an increase in systolic pressure may induce ventricular ectopy even though the left atrial pressure remains low; on the other hand, raising the atrial pressure does not induce ectopic rhythms unless associated with an increase in arterial pressure. This phenomenon (mechanoelectrical association or contraction-excitation feedback) seems to be a direct one not mediated by either ischaemia or adrenergic stimulation. Both refractoriness and intraventricular conduction are affected by mechanical loading, although the direction of change depends on several factors. The mechanism of pressure-related arrhythmias remains obscure. Triggered activity due to early after-depolarizations is one possibility. Ventricular arrhythmias observed in chronic hypertension might be a clinical manifestation of mechano-electrical association, especially when they occur in conjunction with acute blood pressure elevations. Several antihypertensive agents with different mechanisms of action also have an antiarrhythmic effect. Extensive research to establish the antiarrhythmic effectiveness of antihypertensive treatment in cases with ventricular arrhythmias is still warranted.

Atrial late potentials: paroxysmal supraventricular tachycardia versus paroxysmal atrial fibrillation

The atrial signal averaged electrocardiogram has been used to detect patients at risk for paroxysmal atrial fibrillation but not yet for paroxysmal supraventricular tachycardia. The P-wave-triggered signal-averaged electrocardiogram, during sinus rhythm, was obtained from 97 subjects divided in groups as follows: 30 controls (Group C), 38 patients with documented paroxysmal atrial fibrillation (Group A) and 29 with documented paroxysmal supraventricular tachycardia (Group B). The atrial duration, root mean square of last 20 and 30 ms and the P-QRS segment were measured. Atrial late potentials were considered to exist when: atrial duration was > 120 ms and root mean square of last 20 ms were < 3.5 microV. The atrial duration (ms) was significantly shorter (P < 0.001) in Group C (113.4 +/- 8) than in Group A (138.5 +/- 23.8) and Group B (134.3 +/- 14.3). The root mean square (microV) of last 20 ms was significantly higher (P < 0.001) in Group C (5.2 +/- 2.5) than in Group A (2.5 +/- 1.3) and Group B (3.1 +/- 1.8). Atrial late potentials were present in 3/30 controls, 32/38 of Group A cases and 23/29 of Group B. The specificity and sensitivity were, respectively: 0.90, 0.84, for Group A, and 0.90, 0.79 for Group B. The P-QRS segment (ms) was significantly shorter (P < 0.01) in Group B (12.5 +/- 9.4) than in Group C (32.5 +/- 16.9) and Group A (20.5 +/- 13.4).(ABSTRACT TRUNCATED AT 250 WORDS)

Susceptibility of the right and left canine atria to fibrillation in hyperglycemia and hypoglycemia

The objective of this study was to investigate the changes in the refractory period and in the susceptibility to fibrillation of canine atria associated with different levels of glycemia, and the differences in these parameters between the two atria. In 20 anesthetized, open-chest dogs weighing 24 kg, the effective refractory period was measured by atrial pacing with a run of 8 stimuli (S1-S1 350 ms) followed by a progressively earlier S2 until no stimulation of the atrial tissue occurred. The susceptibility to fibrillation was assessed by applying DC at 2, 3, and 4 V for 3 seconds, 7 times each, on the atrial appendage. If fibrillation occurred and persisted for 3 minutes, a transthoracic synchronized shock was delivered (200 J). The refractory period and the susceptibility to fibrillation were assessed under normoglycemia first, and then under hypo and hyperglycemia, in the right and left atrium successively, in random order. The incidence of induced atrial fibrillation in the right atrium was: hypoglycemia 31.96% (132 of 413 attempts); normoglycemia 24.11% (81 of 336; p < 0.05); and hyperglycemia 20.23% (85 of 420). Results for the left atrium were hypoglycemia 52.06% (215 of 413); normoglycemia 40.18% (135 of 336; p < 0.005); and hyperglycemia 32.86% (138 of 420; p < 0.05). Sustained atrial fibrillation (> 3 minutes) occurred significantly more often under hypo rather than hyperglycemia and stimulated the left rather than the right atrium. The refractory period was shortest under hypoglycemia in the left atrium and longest under normo or hyperglycemia in the right atrium.(ABSTRACT TRUNCATED AT 250 WORDS)

Anatomical origin of pressure-related ventricular ectopic rhythms

In order to determine the origin of pressure-related ectopic rhythms, the main arteries were clamped in 11 anesthetized dogs, or the arteries or veins were transfused, while on or off metaraminol. The epicardial right atrial electrogram, the intracavity electrograms and the pressure of the two ventricles were recorded. Sinus rhythm was associated with 64/64 (100%) of the control periods off metaraminol, but only 19/50 (38%) of the clamping of the main arteries (P << 0.0005). In 14/27 aortic clampings ectopic beats appeared from the left ventricle and in 13/27 from the right one. In 4/23 clampings of the pulmonary artery ectopic beats appeared from the left ventricle and in 15/23 from the right one (P < 0.05). Sinus rhythm was associated with significantly lower left ventricular systolic pressure than any ventricular arrhythmia. The left ventricular systolic pressure associated with ectopic rhythms from the left ventricle was significantly (P < 0.005) higher than that associated with those from the right ventricle. The right ventricular systolic pressure during sinus rhythm was significantly (P < 0.005) lower than that during ectopic rhythm from any ventricle. It is concluded that a rise in the pressure of one ventricle tends to cause ventricular ectopic rhythms originating predominantly, but not exclusively, from this ventricle. The origin of ventricular ectopic rhythms from the right ventricle does not preclude that the arrhythmia may respond favorably to lowering of the systemic pressure.

The circadian profile of extrasystolic arrhythmia: its relationship to heart rate and blood pressure

This paper aims at examining whether there is an association between the circadian patterns of systolic blood pressure, heart rate and the incidence of ventricular ectopic beats, as well as to confirm that reducing the blood pressure by a diuretic may also reduce the ectopic frequency. Thirty-four ambulatory patients with ventricular ectopic beats and a systolic blood pressure of 131.33 +/- 17.46 mmHg had a 24-hour Holter electrocardiographic and blood pressure monitoring following 1 week off any antiarrhythmic and antihypertensive treatment. Then they received for one week a standard diuretic combination (amiloride 5 mg + hydrochlorothiazide 50 mg) at a dose depending on their systolic pressure value and their monitoring was repeated. The mean hourly values of systolic blood pressure, heart rate and ventricular ectopic beats were "normalized", i.e. expressed as (x-x)/SD, taking each patient's 24-hour average as zero and his own standard deviation as the unit of measurement. As a group, there was an independent positive correlation between blood pressure and ectopic beats, while the heart rate was a nonsignificant negative factor for ectopic beats. On an individual level, however, an independent positive significant correlation between blood pressure and ectopic beats was found in only 8 cases, with a negative one in 4 cases. While the blood pressure of the group ranged symmetrically around its daily average value, the corresponding ectopic beat curve was highly asymmetric, with a very high incidence (up to 2.56 +/- 0.52 SD) for a rather short time (only 9.41 +/- 3.56 hours above average) and a low incidence (up to 1.26 +/- 0.49 SD) for the remaining 14.59 hours below average. Sudden rises in ectopic beat (greater than 1 SD/hour) occurred 1 to 6 times per day in each individual, significantly (P less than 0.01) more often (20.31%) with a high (greater than 1 SD) blood pressure than with a low (less than -1 SD) one (8.99%) with intermediate frequencies at intermediate pressures. After treatment with the diuretic, the systolic blood pressure was reduced, the heart rate increased and the ventricular ectopic beat incidence reduced (significant changes). The mean change in systolic pressure in 25 patients with a reduction in ectopy was a significant (P less than 0.01) decrease (-5.21 +/- 8.70 mmHg) while in the remaining 9 cases there was a non significant increase (+1.68 +/- 7.63 mmHg). The heart rate was higher in both subgroups.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of group psychosocial intervention on coronary risk factors

The purpose of this study was to investigate whether a psychosocial intervention approach aimed at resolving psychological conflicts could reduce the severity of risk factors for post-acute myocardial infarction patients. Twenty-three patients with a recent myocardial infarction participated in a group psychosocial intervention program which lasted 1 year. Twenty other patients with recent myocardial infarction served as controls. Patients form both groups had regular clinical and laboratory follow-up as well as medication. Mean values for seven risk factors of coronary heart disease (smoking, S; body weight, W; serum cholesterol, C; triglycerides, T; systolic and diastolic blood pressure, SBP, DBP; serum uric acid, U) were compared between the two groups in the 1st, 3rd, 6th and 12th months of the follow-up. The maximal mean improvements of the study versus the control group were as follows: W: -2.82 vs. -1.05 kg; C: -56.04 vs. -6.25 mg/dl; T: -20.61 vs. -2.4 mg/dl; U: -0.57 vs. -0.9 mg/dl; S at 1 year -55.5 vs. -10%. It is concluded that group psychosocial intervention with post-acute myocardial infarction patients considerably reduces some coronary-disease risk factors.

Pressure-related ventricular tachycardia

A case with syncope on exertion and paced heart block is presented. Non-sustained ventricular tachycardia was seen on Holter monitoring and reproduced repeatedly by either exercise or an injection of an alpha agonist, but not with provocative electrophysiology. Antihypertensive treatment using a beta-blocker with endogenous sympathomimetic activity prevented recurrences. It is suggested that this is a case of pressure-related tachycardia.

Response of tertiary centres to pressure changes. Is there a mechano-electrical association?

STUDY OBJECTIVE

To investigate the mechanism of pressure related ventricular arrhythmias by examining them during atrioventricular (AV) block.

DESIGN

Complete AV block, where all ventricular beats are ectopic, was induced by AV node ablation and/or by toxic digitalisation, and rhythm changes were studied while arterial blood pressure was repeatedly raised and lowered.

SUBJECTS

15 anaesthetised mongrel dogs, weight 15-28 kg, were used. AV block was induced in eight by chemical or mechanical ablation of the AV node. In five of these and in seven other dogs, 5.0-7.5 mg digoxin was also given.

MEASUREMENTS AND RESULTS

Following AV block due to ablation, a heart rate increase (or no change) was found in 87.5% of 56 arterial pressure increases produced by elevation of an open arterial blood reservoir or by metaraminol infusion, but in only 21.8% of 55 pressure decreases caused by arterial bleeding (p much less than 0.001). Following AV block due to digitalisation, the equivalent figures were 96% of 50 pressure increases and 27.3% of 55 pressure decreases (p much less than 0.001). While arterial pressure was increased there was moderate acceleration of the escape rhythm, then appearance of premature ventricular beats, then non-sustained and finally sustained ventricular tachycardia. The reverse occurred, with some hysteresis, on decreasing the arterial pressure. In five of the digitalised animals, arterial pressure reduction to nearly zero caused reproducible sudden arrest, with resumption of the ordinary escape rhythm on increasing the pressure again.

CONCLUSIONS

The findings suggest the possibility of two kinds of ectopic rhythm in AV block: the "normal" escape rhythm which is only moderately affected by arterial pressure changes; and an "abnormal" faster pressure dependent rhythm which is generated by high arterial pressure and abolished by pressure near zero, as if there were a mechano-electrical association. This abnormal rhythm may prevail completely in digitalis toxicity so that if cardiac arrest occurs, no automaticity can be expected to appear unless arterial pressure is raised.

Arrhythmogenic effect of high blood pressure: some observations on its mechanism

An increase in aortic pressure is a reproducible way of causing ventricular ectopic rhythms. This study sought to determine whether it is the aortic pressure per se or the concommitant increase in afterload or preload that has a direct arrhythmogenic effect. Experiments were carried out in 17 anaesthetised dogs. For each 10 s period the pressure and the presence of a ventricular arrhythmia (at least one ectopic beat) were noted. In nine animals an aortic valve gradient was created (and released). The results were compared to those obtained by impeding the aortic flow at the ascending aorta. The mean systolic left ventricular pressure was significantly higher in the arrhythmia associated periods in 8/9 experiments when there was an aortic valve gradient and in 5/9 experiments when there was not. In 4/9 experiments the mean aortic pressure associated with arrhythmia was significantly lower with an aortic valve gradient than when there was no gradient and no arrhythmia. In 7/9 of these experiments, coronary sinus flow was measured volumetrically during the manoeuvres applied. The coronary flow was significantly lower when there was neither arrhythmia nor aortic valve gradient than when there was an arrhythmia (with or without an aortic valve gradient). In another eight experiments a pressure reservoir in the aorta was either raised or lowered while another pressure reservoir in the left atrium was moved in the opposite direction. Thus the mean aortic pressure could be increased while the left atrial pressure was decreased and vice versa. If the left atrial pressure was taken into account, the mean difference of the aortic pressure from its expected value, derived from the aortic v left atrial pressure regression equation, was significantly higher when there was an arrhythmia than it was when there was no arrhythmia in all eight experiments. On the other hand, the mean difference in the left atrial pressure from its expected value was significantly higher when there was an arrhythmia in 1/8, lower in 2/8 and not significantly different in 5/8 experiments. It is concluded that when the blood pressure is raised, it is the increase in afterload rather than an increase in aortic pressure itself or in the preload that has an arrhythmogenic effect on the ventricles.

Effect of acute hypertension on the cardiac rhythm. Experimental observations

An acute increase in blood pressure (BP) may be associated with the genesis of ventricular ectopy. Fourteen anesthetized dogs were examined to find out whether the critical pressure that causes an arrhythmia may be an index of the tendency of the myocardium to generate ectopic rhythms. An acute change in BP was produced 321 times using an arterial pressure reservoir or aortic obstruction or a metaraminol infusion or, inversely, arterial bleeding. Each time the BP was increased, cardiac arrhythmias appeared and each time the BP was decreased the cardiac arrhythmias disappeared. The most common type of arrhythmia was ventricular ectopy (123/167 acute BP increases), usually in a form of bigeminy. The next most common rhythm disturbance was atrioventricular block (32/167 acute BP increases), especially when a constant rate was achieved by atrial pacing. The BP above which an arrhythmia appeared varied greatly among different animals (189.0 +/- 55.1 mmHg, means +/- SD). It was significantly (p less than 0.01) reduced (-29.0 +/- 17.1 mmHg) following coronary ligation and significantly (p less than 0.05) raised (+/- 41.6 +/- 38.7 mmHg) following lidocaine administration. The incidence of ventricular ectopy on increasing the BP was significantly higher at low heart rates in ten experiments, lower in two and not significantly different in 14. The incidence of premature ventricular complexes, the degree of atrioventricular block and the PR interval in first-degree atrioventricular block, whenever these rhythm disorders appeared, were a function of the BP level. It is concluded that an acute increase in BP may cause rhythm disturbances, usually in the form of ventricular ectopy and/or atrioventricular block.(ABSTRACT TRUNCATED AT 250 WORDS)

An extravascular hydraulic system to control blood pressure by a feedback regulation of the venous return

Since increases in blood pressure may be effectively controlled by hydraulic feedback by reducing the venous return through the inferior vena cava in proportion to the blood pressure this principle was applied using a totally implantable extravascular system consisting of a periaortic blood pressure sensor and a pericaval cuff around the inferior vena cava. The two cuffs were supported externally by hard skeletons, filled with water, and connected directly to each other. The two devices were tested separately and together in 10 anaesthetised mongrel dogs with normal and high blood pressure induced by a metaraminol infusion. With the periaortic sensor an increase in blood pressure of 100 mmHg caused a mean(SD) isotonic volume displacement of 0.41(0.11) ml, and an increase in the pericaval balloon energy content of 100 ml.mmHg-1 caused a fall in blood pressure of 37.8(18.3)%. The whole system prevented an excessive rise in blood pressure when metaraminol was infused, with a feedback gain of about 2.8. It is concluded that blood pressure can be maintained at acceptable levels despite strong hypertensive stimuli, by this system, without additional treatment with drugs or an external energy source. The system is totally implantable and is applied extravascularly so that no anticoagulation is needed.

Acute changes in blood pressure as a cause of cardiac arrhythmias

The effect of an acute change in blood pressure (BP) on ventricular ectopic activity and the influence of antiarrhythmic agents on this effect were examined in 24 patients. In 11 patients with premature ventricular complexes (PVCs), the BP was temporarily reduced by a sodium nitroprusside drip. In all of them the incidence of PVCs was reduced (or annihilated) by the induced hypotension. In 13 patients without ventricular ectopic activity, a metaraminol drip was given until either a PVC appeared or the systolic BP reached 200 mmHg, or symptoms appeared. In 12 cases at least one PVC appeared and in 8 of them the total number of PVCs was 13 or more, usually in the form of bigeminy. The repetition of the test following quinidine administration (serum quinidine level 1.7 +/- 0.5 ng ml-1) in 6 cases did not change this pattern, with one exception. It prevented the appearance of idioventricular accelerated rhythm in one case in whom this rhythm had been induced by the hypertension provocative test before the quinidine administration. All cases, in whom the test failed to induce more than 3 PVCs, had no cardiac problem at all. Six of the 8 cases in whom the test induced 13 or more PVCs had organic cardiac disease or palpitation. Other arrhythmias observed on BP elevation, were supraventricular extra beats, nodal escape rhythms and atrioventricular block. In one case with cardiomyopathy, the BP elevation was associated with early signs of heart failure that subsided quickly. In conclusion, acute elevation on BP may be associated with the generation of PVCs and its reduction with their reduction or disappearance.

Torsade des pointes and aprindine

Aprindine was given orally to an 88-year-old patient with atrial fibrillation and ventricular premature depolarizations. The premature beats disappeared and sinus rhythm was restored on the third day of treatment. While on aprindine the QT interval was prolonged and the U wave became very prominent. The aprindine was stopped but 36 hr following the last oral dose, ventricular arrhythmia appeared with the characters of torsade des pointes. Three such episodes occurred within 24 hr. It is suggested that aprindine both eliminated the premature depolarizations and rendered the myocardium vulnerable by prolonging the QT interval. On discontinuing the medicament the premature beats reappeared while the myocardium was still vulnerable, so that torsade des pointes resulted.

For debate . . . Individual contributions to multiauthor papers

The curricula vitae of four candidates for a professorial appointment at Athens University were examined to estimate the actual contribution of each candidate to the papers of which he was a coauthor. A total of 879 research papers by the four candidates were analysed in terms of the number of authors, the sequence of names, and the year of publication. The four authors presented 364, 349, 96, and 70 papers. If an equal contribution of all coauthors is assumed, the actual number of papers (all papers divided by the number of authors), is about 106, 83, 28, and 26, respectively, so that the rank of the four candidates did not change. On the assumption that the contribution was related to the candidate's position in the order of the coauthors' names, the numbers of papers were corrected to 84, 95, 26, 33 using one statistical method and to 88, 94, 28, 31 using another. These assumptions may not be valid, however, especially as the last author may be more important than the intermediate ones. It is suggested that the journals require authors to state their specific contribution to a paper, such as original idea, planning, collecting data, writing up, etc.