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PubMed1988

The P wave in the magnetocardiogram.

The P wave of the magnetocardiogram (MCG) was investigated in normal subjects and in patients with right and left atrial overloading. In normal subjects, the MCG P wave was positive at right lower sternal sites and negative in the other portions. The current source deduced from the MCG and the isomagnetic map was directed inferiorly and to the left throughout the entire phase of atrial activation. In patients with right atrial overloading, the direction of the current source deduced from the MCG was similar to that of normal subjects, but its amplitude was significantly greater. In left atrial overloadings, a negative-positive biphasic P wave was seen more frequently than in normal subjects at left parasternal sites. In the late phase of atrial activation, the MCG could detect the two dipoles, i.e. one directed inferiorly and other directed to the left. These dipoles might correspond to right and left atrial activities, respectively. These results show that the MCG might add useful information on current source to the conventional electrocardiogram.

Adult↗
PubMed1977

Detector electrode introduced by mediastinoscopy for atrial triggered cardiac pacing. A follow-up of electrode function in 82 patients.

An atrial detector electrode was introduced by mediastinoscopy in 82 patients requiring permanent cardiac pacing. There were no complications. An adequate P wave was recorded in 80 patients. During the following week, the P wave became ineffective in 5 patients; angina occurred in 2 and atrial arrhythmias in 2. Atrially triggered ventricular pacing established in 73 patients and was followed in 71 patients for a period of 1 to 113 months. In 17 cases, it had to be terminated because of an ineffective or unstable P wave,in 6 cases because of atrial arrhythmias, and in 4 cases because of advanced age and recurrent infections. The method is technically simple and place little stress on the patient.

Adult↗
PubMed1988

Depression of systolic and diastolic myocardial reserve during atrial pacing tachycardia in patients with dilated cardiomyopathy.

Previous reports have shown that increases in heart rate may result in enhanced left ventricular (LV) systolic and diastolic performance. To assess whether this phenomenon occurs in the presence of depressed LV function, the effects of pacing on LV pressure and volume were compared in seven patients with dilated cardiomyopathy (LV ejection fraction 0.19 +/- 0.11) and six patients with no or minimal coronary artery disease (LV ejection fraction 0.69 +/- 0.11). Patients with normal LV function demonstrated significant increases in LV peak-positive dP/dt, LV end-systolic pressure-volume ratio, LV peak filling rate, and a progressive leftward and downward shift of their pressure-volume diagrams, compatible with increased contractility and distensibility in response to pacing tachycardia. There was no change in LV peak-negative dP/dt or tau. Patients with dilated cardiomyopathy, in contrast, demonstrated no increase in either LV peak-positive dP/dt or the end-systolic pressure-volume ratio, and absence of a progressive leftward shift of their pressure-volume diagrams. Moreover, cardiomyopathy patients demonstrated no increase in LV peak-negative dP/dt or LV peak filling rate and a blunted downward shift of the diastolic limb of their pressure-volume diagrams. Tau, as determined from a derivative method, became abbreviated although never reaching control values. We conclude that patients with dilated cardiomyopathy may demonstrate little or no significant enhancement in systolic and diastolic function during atrial pacing tachycardia, suggesting a depression of both inotropic and lusitropic reserve.

Cardiac Output↗
PubMed1993

Improvement in left ventricular function by ablation of atrioventricular nodal conduction in selected patients with lone atrial fibrillation.

Left ventricular (LV) function was studied in 30 patients with lone atrial fibrillation (AF) (paroxysmal [n = 27] and persistent [n = 3]) before and after ablation of atrioventricular conduction. In all patients, drug treatment did not control ventricular rate during AF or prevent recurrences of the arrhythmia, or both. LV ejection fraction, and LV end-systolic and end-diastolic, and left atrial dimensions were measured by echocardiography before (mean 7 +/- 10 months, range < 1 to 37) and after (14 +/- 20 months, < 1 to 77) ablation. Before ablation, LV ejection fraction was < or = 50% in 12 patients (group I) and > 50% in 18 (group II). After ablation, LV ejection fraction increased significantly in group I from 43 +/- 8% to 54 +/- 7% (p < 0.0001). There were also significant decreases in LV-end systolic and end-diastolic, and left atrial dimensions. No changes in these parameters were observed in group II. Groups I and II had a significant difference in the duration of AF (group I: mean 11 years, range 8 to 28; and group II: 5 years, 2 to 14) (p < 0.05). No difference was present in age, sex, New York Heart Association functional class for dyspnea, or type of ablation procedure. Thus, some patients with lone AF may show deterioration of LV function, which appears to be related to the duration of the arrhythmia; in these cases, LV function may improve significantly after ventricular rate control is accomplished by ablation of atrioventricular conduction.

Adult↗
PubMed1988

5-Aminobenzimidazole inhibits gastric acid secretion in Shay-rats.

Benzimidazole and some of its derivatives as 4-nitro and 5-nitro-benzimidazoles, 2-amino-, 4-amino- and 5-aminobenzimidazoles have been tested on gastric acid secretion in Shay-rats. Only 5-aminobenzimidazole decreased the gastric secretory process basal or stimulated by betazole. The antisecretory properties of 5-aminobenzimidazole seem to be linked to an anti H2-histamine activity, since this compound depresses the amplitude of contractions of guinea pig isolated auricle stimulated by betazole. The antisecretive activity appears to be associated to a definite distance between the amino group and the imidazolyl nitrogen, since it appears only when the amino function is located in position 5 of the benzimidazole structure.

Animals↗
PubMed1986

Functional-morphological studies on in vitro cardionatrin release.

Atrial natriuretic peptides (ANP) are hormones produced by the heart atrial cardiocytes in mammals. The main function of these peptides appears to be that of modulating the actions of the renin-angiotensin-aldosterone system. In the rat ANP are stored within specific atrial granules, mainly as a 126-amino acid peptide (cardionatrin IV) which is processed to a 28-amino acid peptide (cardionatrin I) just prior to or during release from cardiocytes. Development of an isolated perifused rat atria preparation has allowed quantitative and qualitative studies on ANP release. Increasing mechanical load in this preparation gives an increased rate of release of immunoreactive cardionatrin. This finding suggests that there is an intrinsic 'stretch-secretion coupling' in the atria.

Animals↗
PubMed1987

The electrophysiologic effects of propafenone hydrochloride in the neonatal canine.

The electrophysiologic effects of the new antiarrhythmic agent, propafenone, were investigated in 10 mongrel canine neonates, ages 5 to 11 days. Utilizing standard His bundle recording and stimulation techniques, assessments of sinus and atrioventricular (AV) node function and atrial, AV nodal, and ventricular refractory periods were performed prior to (control) and after cumulative intravenous doses of 1, 2, and 4 mg/kg of propafenone. Propafenone depressed the spontaneous heart rate and prolonged the postatrial pacing recovery times. AV nodal function was depressed as manifested by Wenckebach periodicity occurring at slower pacing rates, increases in AV nodal conduction time, and increases in AV nodal refractoriness. Atrial and ventricular refractory periods were prolonged significantly in a dose-dependent fashion. Prolongation of the His-Purkinje conduction time occurred at the highest dose. Thus, propafenone exerts a generalized depressant effect on neonatal myocardial conduction and refractoriness which suggests that this agent may be useful in the therapy of atrial and ventricular dysrhythmias in the immature heart.

Animals↗
PubMed1995

Extended transseptal versus conventional left atriotomy: early postoperative study.

BACKGROUND: Mitral valve operations require excellent exposure. The description of an extended vertical transseptal atriotomy by Guiraudon and associates promises to provide optimal exposure of the mitral valve. A prospective study was carried out to evaluate the merits of the extended vertical transseptal atriotomy in comparison with the conventional left atriotomy for mitral valve operations. METHODS: Conventional atriotomy was performed in 24 patients (group I) whereas 65 patients underwent the extended vertical transseptal offroach (group II). They were similar in age, sex, cause of disease, New York Heart Association functional class, left atrial size, and left ventricular function. The early postoperative rhythm changes in these two groups were compared. Statistical studies to analyze the significance of incidence of junctional arrhythmia in these two groups were carried out. RESULTS: Of the 24 patients in group I, 3 had development of transient junctional rhythm after operation, lasting less than 24 hours. None had this arrhythmia at the time of discharge. Of the 65 patients in group II, junctional rhythm was documented in 25, with a rate of occurrence of 38% (95% confidence interval, 27.6% to 52.2%). At the 6-week follow-up, 3 patients still had this junctional rhythm, with a failure to recover rate of 12% (3 of 25). CONCLUSIONS: The surgical exposure was considered excellent and closure of the atriotomy was thought to be easy in group II. However, this should be balanced against a significant (38%) incidence of transient junctional rhythm in the early postoperative period in group II, probably from injury to sinus node artery or atrial conduction pathways.

Adolescent↗
PubMed1985

Effect of nicardipine on left ventricular function and on angina induced by atrial pacing in patients with coronary artery disease.

The effect of intravenous nicardipine, a new calcium antagonist, on haemodynamics, left ventricular function and angina induced by atrial pacing has been investigated in patients with coronary artery disease. Patients were treated with beta-blockers and measurements were made at a fixed heart rate. Nicardipine produced a 24% fall in mean systemic blood pressure (P less than 0.02) and a 37% increase in cardiac index (P less than 0.02). Cardiac filling pressures, dp/dt max and left ventricular ejection fraction were unaltered. The time to pacing induced angina was prolonged (P less than 0.05) when the dose of nicardipine (0.75 mg X min-1) was selected not to cause an excessive fall in blood pressure. Nicardipine is a powerful arteriodilator without detectable negative inotropic effects and prolongs the time to pacing induced angina.

Adrenergic beta-Antagonists↗
PubMed2003

Thrombomodulin and tissue factor pathway inhibitor in endocardium of rapidly paced rat atria.

BACKGROUND: Atrial fibrillation (AF) is well known as one of the cardiogenic causes for thromboembolism. Although decreased flow and hypercoagulable state of the blood in the fibrillating atrium have been emphasized as the underlying mechanisms, endocardial dysfunction in maintaining the local coagulation balance could also contribute to the thrombogenesis in AF. METHODS AND RESULTS: The paroxysmal AF model was created by rapid atrial pacing in anesthetized rats. To test the hypothesis that AF induces local coagulation imbalance by disturbing the atrial endocardial function, the gene expression of intrinsic anticoagulant factors, thrombomodulin (TM) and tissue factor pathway inhibitor (TFPI), were determined by means of ribonuclease protection assay, Western blotting, and immunohistochemistry. Rapid atrial pacing for 8 hours significantly decreased TM and TFPI mRNA levels in the left atrium but not in the ventricle, leading to the downregulation of their immunoreactive proteins. Immunohistochemical analysis revealed that TM and TFPI were expressed predominantly in the endocardial cells of the normal atrium, presumably preventing local blood coagulation, and that rapid atrial pacing induced the loss of TM and TFPI expression in the endocardium, leading to deficiency in anticoagulant barriers between the atria and the blood. CONCLUSIONS: Rapid atrial pacing acutely downregulated the gene expression of TM and TFPI in the atrial endocardium, thereby inducing local coagulation imbalance on the internal surface of the atrial cavity. These results would support the validity of supplement of anticoagulant molecules deficient in AF.

Animals↗
PubMed1976

Atrial receptors in the cat.

Action potentials were recorded from slips of the cervical vagi in anaesthetized cats. Single functional units with atrial patterns of discharge (type A, B and Intermediate) were first obtained and then attempts were made to alter (i.e. convert) their patterns of discharge. Finally the points of origin of their action potentials were located. The investigations were done in five stages. 2. In the first series, thirty unselected units were investigated in thirty cats. Twenty-five of these were located in the endocardium of vein-atrial system and consisted of two type A, fifteen type B and eight Intermediate type units. The remaining five units were located elsewhere in the chest Conversion of the pattern of discharge was achieved in sixteen of the twenty-five atrial units. Both atrial type A units were converted. 3. In the second series, eight type A units were selectively studied in twelve cats. Five were located in the atrial endocardium and all were converted. Of the other three units which were located at other sites in the chest, one could not be converted. 4. In the third series, four type A units which could not be converted were selectively studied in twenty cats. All were located outside the atria. 5. In the fourth series, three type B units which could not be converted were selectively studied in six cats. These units were located in the pulmonary veins and in the lateral walls of the atria. 6. In the fifth series, fifty-five units were investigated in three anaesthetized spontaneously breathing cats. The proportion of the types of units were similar to that obtained in the artificially respired cats (first series). 7. The present study has shown that atrial receptors with a type A pattern of discharge are relatively rare in the cat and that conversion of the patterns of discharge is a common phenomenon. Evidence is presented which suggests that there is one basic type of atrial receptor whose pattern of discharge is determined by their precise location in the vein-atrial system.

Action Potentials↗
PubMed2002

[Results of isolated and combined surgical coronary revascularization in patients over 75].

BACKGROUND: Increase in life expectancy is causing an increase of surgical myocardial revascularization procedures in the elderly. We evaluate the evolution of this type of interventions in people older than 75 years, taking into account the risk factors, results and survival. PATIENTS AND METHOD: Between July 1988 and May 2001, 237 isolated or combined myocardial revascularization procedures were carried out in patients older than 75 years (Group I), while 1177 were performed in younger patients (Group II). We retrospectively analyzed the mortality risk factors, surgical procedures, postoperative complications and survival in Group I patients. RESULTS: Preoperatively, Group I patients showed a more frequent left ventricular dysfunction, left main coronary stenosis, emergency surgery and combined procedures, while Group II patients displayed more common preoperative myocardial infarction and dyslipemia. Mortality in Group I was 20.7% vs 9.09% in Group II. Mortality was higher for mixed procedures (27.1%) than for isolated myocardial revascularization (13.8%). Postoperative complications were present in 48.5% patients. Significant preoperative risk factors of mortality in Group I were: female sex, high-risk ergometry, III-IV NYHA functional class, and atrial arrhythmia. The preoperative NYHA functional class was also a morbidity risk factor. Survival at 1, 3 and 5 years was present in 98.4%, 92.1% and 81% patients, respectively, NYHA functional class I-II being present in 94.18% patients. CONCLUSIONS: Myocardial revascularization surgery in people older than 75 years leads to an increase of morbimortality. Anyway, long-term survivors' quality of life makes us think of surgery as a valid treatment alternative.

Adult↗
PubMed2001

Characterization of reentrant circuit in macroreentrant right atrial tachycardia after surgical repair of congenital heart disease: isolated channels between scars allow "focal" ablation.

BACKGROUND: The purpose of this study was to characterize the circuit of macroreentrant right atrial tachycardia (MacroAT) in patients after surgical repair of congenital heart disease (SR-CHD). METHODS AND RESULTS: Sixteen patients with atrial tachycardia (AT) after SR-CHD were studied (atrial septal defect in 6, tetralogy of Fallot in 4, and Fontan procedure in 6). Electroanatomic right atrial maps were obtained during 15 MacroATs in 13 patients, focal AT in 1 patient, and atrial pacing in 2 patients without stable AT. A large area of low bipolar voltage (</=0.5 mV) involved most of the free wall in all patients and contained 2 to 7 dense scars or lines of double potentials, forming 29 narrow channels (width </=2.7 cm) between scars in all but 1 patient, who had a single scar and only focal AT. All 15 MacroATs were propagated through narrow channels. Ablation within the channel eliminated all 15 MacroATs with 1 to 3 (median 1) radiofrequency applications. Ablation was performed in 9 other channels identified during MacroAT (5 patients) and in 5 channels identified during atrial pacing (2 patients). Conduction block was obtained across 28 of 29 channels. After ablation, reproducible sustained right AT was not induced in any patient. During follow-up (median 13.5 months), new MacroATs, atrial fibrillation, or palpitations occurred in 3 of 16 patients. CONCLUSIONS: MacroAT after SR-CHD requires a large area of low voltage containing >/=2 scars forming narrow channels. Ablation within the channels eliminates MacroAT.

Adult↗
PubMed1989

Chronotropic responses of chick atria to field stimulation after various neural crest ablations.

Three models of altered autonomic innervation of the chick heart have been developed in the last few years. These include sympathetically aneural heart, parasympathetically aneural heart, and heart with cholinergic innervation reconstituted from the nodose placodes. The neural status of these hearts has been assessed by a variety of morphological and biochemical methods, but the functional status of innervation is not known. In the present study, we have used electrocardiography and field stimulation to determine the functional neural status of the three different innervation models. The RR and QTc intervals were measured to assess the dominant autonomic tone and autonomic dysfunction in the heart. Even though the RR and QTc intervals were found to be identical in sham and experimental embryos, field stimulation of superfused atria showed that the sympathetically aneural heart has functional cholinergic innervation but lacks any sympathetic response. Hearts from embryos which were parasympathetically aneural lacked a cholinergic response to field stimulation and were judged to be functionally parasympathetically aneural. Hearts with cholinergic ganglia reconstituted from the nodose placodes have normal RR and QTc intervals as well as a normal cholinergic response to field stimulation. The results indicate that these neurons are functionally indistinguishable from neural crest-derived neurons.

Action Potentials↗