Biomedical subjects

Manlio F Márquez

Publications and source records attributed to Manlio F Márquez.

At least 19 recordsLinked to original sources

PubMed2006

Cerebrovascular blood flow during the near syncopal phase of head-up tilt test: a comparative study in different types of neurally mediated syncope.

AIMS: This study analyses the changes in cerebral blood flow (CBF) velocity occurring in the near syncopal phase of head-up tilt test (HUT) to determine whether their appearance during the premonitory symptoms permits the differentiation of the different types of haemodynamic response. METHODS AND RESULTS: Six hundred and nineteen patients aged 35.9 +/- 16.4 with a prior history of syncope (55%) or presyncope (45%) were studied. Head-up tilt test was positive in 585 patients. The test was interrupted before syncope, once hypotension was evident and CBF changed. A vasovagal reaction (VVR) was observed in 245 patients. They had a 59% fall in diastolic CBF velocity, whereas systolic CBF velocity decreased by 12%. Postural orthostatic tachycardia syndrome (POTS) was observed in 82, systolic and diastolic CBF velocity decreased 44 and 60%, respectively. A similar response was observed in 258 patients with the orthostatic intolerance (OI) pattern. No significant changes were observed in the negative group. CONCLUSION: Patients with VVR had changes in CBF velocity, which are different from those presented by patients with POTS and OI pattern. Cerebral blood flow monitoring is useful to increase the yield of HUT and may allow early interruption before syncope occurs, reducing patient discomfort.

Adolescent↗

PubMed2005

Neurocardiogenic syncope in chronic atrioventricular block.

We report a 37-year-old man with type I second-degree atrioventricular (AV) block (atypical Wenckebach's periodicity) referred to our department for pacemaker implantation because of an episode of syncope. After exhaustive evaluation, including electrophysiological test, in which Wenckebach's cycles with block within the AV node was demonstrated, syncope was considered to be neurally mediated. Head-up tilt testing with sublingual isosorbide dinitrate was positive. The decrease in atrial rate at the beginning of the vasovagal reaction was not immediately accompanied by a depressed AV node conduction. Only at the moment of syncope did incomplete AV block appear. This observation illustrates (1) a neurally mediated origin of syncope in a patient with chronic AV block, and (2) the different time-course responses of the sinus and AV nodes to autonomic tone.

Adult↗

PubMed2005

Age, body mass index, and menstrual cycle influence young women's heart rate variability --a multivariable analysis.

Heart rate variability (HRV) in women has been related independently to endogenous sex hormones, hormone replacement therapy, menopause, menstrual cycle, body mass index (BMI), and physical conditioning. However, the joint influence of all these factors has not been reported. The present study describes the relation between circadian variation HRV and assesses its association with BMI, age, and menstrual cycle in healthy young women. A multivariable analysis was performed to estimate the predictive variables involved in SDNN, pNN50, and rMSSD profile, using the classification and regression tree (CART) and the logistic regression models. It was found that the first predictive variable was age, which divided women in two groups: >29.5 years old and <29.5 years old. In the case of the SDNN, the second predictive variable was BMI; the highest values were observed in women younger than 23 years old, with a BMI less than 19.82 kg/m2 and during the follicular phase of her menstrual cycle. For pNN50 and rMSSD the second predictive variable was menstrual cycle for women younger than 29.5 years old. Thus, in this group of women, age was a major determinant of cardiac autonomic nervous modulation followed by the BMI. HRV may be better understood using a multivariable analysis that could mimic physiological conditions.

Adult↗

PubMed2005

Familial vasovagal syncope.

Vasovagal syncope (VVS) is a common clinical problem characterized by transient episodes of loss of consciousness due to abnormal autonomic activity. This paper describes two groups of monozygotic twins, from different families, affected by VVS and a family with several members with this condition. Their clinical characteristics, haemodynamic response to tilt, treatment, and outcome are described.

Adult↗

PubMed2005

Dynamic electrocardiographic changes after aborted sudden death in a patient with Brugada syndrome and rate-dependent right bundle branch block.

A 37-year-old man with Brugada syndrome and dynamic changes of the ST-segment morphology observed after an episode of aborted sudden death is described. On admission, after 3 syncopal episodes during nighttime, his electrocardiogram showed right bundle branch block (RBBB) with a J-point elevation of 0.6 mV in lead V 2 . Changes observed in the following days included a diminished J-point elevation and intermittent "saddle-back" type of morphology. During a previous 2-year follow-up, intermittent, complete, acceleration-dependent RBBB was documented. Right ventricular intracavitary tracings showed an RS pattern with a broad S wave in the unipolar electrogram; the time of onset of intrinsic deflection in this electrogram was 60 milliseconds. To our knowledge, this is the first report of an intracavitary demonstration of complete RBBB in Brugada syndrome.

Adult↗

PubMed2005

Arrhythmic storm responsive to quinidine in a patient with Brugada syndrome and vasovagal syncope.

A 37-year-old man with Brugada syndrome (BrS) and arrhythmic storm is described. One month after implantation of a cardioverter-defibrillator he presented with recurrent appropriate shocks for spontaneous ventricular fibrillation (VF). Because of this arrhythmic storm, quinidine therapy was initiated with total suppression of all spontaneous arrhythmias. He had remained free of arrhythmias for 22 months since quinidine initiation. Two episodes of VF occurred after the patient stopped taking the medication. The patient resumed quinidine and has been free of VF for the last 3 months. This response to quinidine in a patient with symptomatic BrS supports its role in the prophylaxis of arrhythmic events in BrS.

Adult↗

PubMed2005

Drug therapy in Brugada syndrome.

Sudden cardiac death in healthy individuals with structurally normal hearts and a characteristic morphology of the QRS complex resembling a right bundle branch block with elevation of the ST segment in V1 to V3 is known as Brugada syndrome (BrS). Although placement of an implantable cardioverter-defibrillator is considered the only effective therapy for symptomatic patients, some authors have repeatedly reported a beneficial effect of quinidine and isoproterenol in patients with BrS. Also, isolated case reports on the usefulness of cilostazol, sotalol, and mexiletine have been described. The present article reviews the mechanisms by which these drugs may act and their role in the pharmacotherapy of BrS. Other possible agents, mainly I(2) blockers, are also reviewed.

Bundle-Branch Block↗

PubMed2004

[Myocardial reperfusion injury].

Myocardial reperfusion injury is defined as the adverse effects that ensue upon restoration of the circulation, which allows blood and nutrients to reach cells previously subjected to ischemia. Restoration of blood flow can be accompanied by the release of oxygen free radicals, the appearance of intracellular calcium overload, and alterations in cell metabolism -all situations that can give rise to functional or structural myocardial injury. Clinical signs of injury may appear after circulation is restored or after the use of extracorporeal circulation during heart surgery, and are manifested as stunned or hibernating myocardium after acute coronary syndromes, as the no-reflow phenomenon (microvascular injury) after blood flow is restored during angioplasty or after < >, and especially after surgical revascularization. This review examines the pathophysiological substrates, clinical manifestations and current approaches to treatment for each of these entities.

Animals↗

PubMed2003

Cycle length-dependent repolarization changes during atrial fibrillation in the Brugada syndrome.

This is a case report of a patient with Brugada syndrome who developed paroxysmal atrial fibrillation. During the episode, beat-to-beat changes in ventricular repolarization were observed. These changes were a paradoxical ST-segment alteration after a short-coupled ventricular beat. These findings, not reported before, may be helpful for the diagnosis of this syndrome.

Atrial Fibrillation↗

PubMed2003

Paced breathing can prevent vasovagal syncope during head-up tilt testing.

BACKGROUND: Clinical experience suggests that, through the control of heart rate, paced breathing may prevent syncope. OBJECTIVE: To assess the effect of metronome-paced breathing (0.2 Hz) on the outcome of head-up tilt test (HUT) in patients with vasovagal syncope. PATIENTS AND METHODS: Ten patients (two men), mean +/- SD age 18.4 +/- 5.1 years, with a positive HUT with spontaneous breathing and no evidence of cardiovascular or neurological disease, were exposed to a second HUT under metronome-paced breathing (0.2 Hz). Continuous electrocardiographic recordings were obtained during the two tests, and heart rate variability was analyzed off-line. RESULTS: During HUT with metronome-paced breathing, only one of the 10 patients developed bradycardia, hypotension and syncope (P<0.01, Wilcoxon). Compared with HUT with spontaneous breathing, HUT with paced breathing induced a larger increase in the heart rate in the first minute of tilt (4 +/- 6 beats/min versus 16 +/- 12 beats/min, P<0.05). CONCLUSIONS: The results show that paced breathing can prevent vasovagal syncope induced by HUT. This finding suggests that respiratory training could be useful to prevent vasovagal syncope.

Adolescent↗

PubMed2002

[Syncope of unknown origin in patients with permanent auriculoventricular block with an implanted pacemaker. Usefulness of the tilt table test].

Four female patients aged 26 to 71 years, with permanent complete AV heart block and an implanted pacemaker had syncope or presyncope after the pacemaker implantation. As part of the study protocol the tilt table test was done. Neurological disease, arrhythmias, pacemaker syndrome or dysfunction of the stimulation system were ruled out. A head up tilt was performed, isosorbide was used as pharmacological challenge, since the basal test was negative. In three patients this test was positive: in one patient possibly caused by postural orthostatic tachycardia syndrome, and two with neurally mediated syncope. In one patient it was not possible a diagnosis. The head-up tilt test is a useful procedure to identify the etiology of the appearance of syncope or presyncope after a pacemaker implantation in patients with complete and permanent AV block.

Adult↗

PubMed2002

[Effect of angiotensin blockade on the orthostatic response in patients with systemic arterial hypertension].

INTRODUCTION AND OBJECTIVES: The effect of the treatment of arterial hypertension with angiotensin inhibitors on the autonomic response to orthostatism was studied. PATIENTS AND METHOD: In 20 hypertensive patients, enalapril (10 to 20 mg) was administered daily for four weeks. Then, irbesartan (150 to 300 mg) was given for four weeks. Finally, 10 mg of enalapril combined with 150 mg of irbesartan was prescribed for another four weeks. Heart rate variability at rest and during the head-up tilt test with controlled respiration was assessed at the beginning and end of each period. RESULTS: Mean arterial pressure showed a similar reduction in the three treatment periods. There were no changes in heart rate. Heart rate variability at rest showed differences in the spectral high-frequency component between the control and the treatment periods (p = 0.10). There was an increase in the high-frequency component between the control and the third (p = 0.047) and the fourth periods (p = 0.03). In the head-up tilt test there was a decrease in total spectral high-frequency power. CONCLUSIONS: There was no increase in orthostatic intolerance with these drugs in hypertensive patients. The absence of changes in heart rate in spite of a decrease in blood pressure suggests resetting of the baroreflex function. The long-term control of hypertension with these drugs may have a favorable effect on heart rate variability, with an increase in parasympathetic activity.

Adult↗

PubMed2002

Radiofrequency ablation of atrioventricular accessory pathways associated with discordant atrioventricular connections.

Discordant atrioventricular connections associated with Wolff-Parkinson-White syndrome increase the challenge of radiofrequency ablation. We report the results and techniques of radiofrequency ablation in three patients with discordant atrioventricular connections, including one patient having double outlet right ventricle with atrioventricular reentry tachycardias. There were two males and one female, aged 14 and 22 years old. We found four accessory pathways during our electrophysiological studies, with two of them manifest on the electrocardiogram, corresponding to left paraseptal and right midseptal regions. The electrophysiological study confirmed this localization, and showed two concealed accessory pathways in the right and left paraseptal regions. Radiofrequency ablation was successful in all cases without recurrence at a mean follow-up of 18.6 months. No complications were observed during the procedures. We conclude that radiofrequency ablation is feasible and effective in the ablation of accessory pathways in patients with discordant atrioventricular connections.

Accessory Nerve↗

PubMed2002

Common electrocardiographic artifacts mimicking arrhythmias in ambulatory monitoring.

BACKGROUND: Ambulatory electrocardiographic monitoring is used in clinical practice as a means of detecting cardiac arrhythmias during daily activities. Current equipment provides analysis for the detection of arrhythmias, ST-segment deviation, and more sophisticated analyses (late potentials, Q-T behavior, and heart-rate variability). However, despite the system used, a number of artifacts could mislead diagnosis. METHODS AND RESULTS: We prospectively searched for artifacts during ambulatory electrocardiography in patients referred for monitoring to our institution, a tertiary referral center. Patients were ambulatory at home, work, school, or within the hospital. We divided artifacts according to Krasnow and Bloomfield's classification (pseudoarrhythmia, nonarrhythmia), and we added a new category, artifacts in patients with pacemakers. Artifacts encountered mimicked sinus arrest, supraventricular arrhythmias, ventricular arrhythmias, and aberrancy. Examples of each one and diagnostic clues are provided to recognize these artifacts properly. CONCLUSIONS: A substantial amount of invalid data (false-positive findings because of electrocardiographic artifacts) were identified during ambulatory electrocardiographic monitoring that can lead to inappropriate interpretation and may result in severe diagnostic errors.

Arrhythmias, Cardiac↗

PubMedDate not supplied

Vestibular function interferes in cardiovascular reflexes [corrected].

BACKGROUND: Experimental work indicates that the vestibular system participates in autonomic reflexes during body movement and postural changes. However, there are no studies of cardiovascular reflexes during vertigo due to human acute vestibular lesions. METHODS: We assessed the response to active change of posture and hand immersion in cold water in seven patients with unilateral peripheral vestibular failure (vestibular neuritis) and seven age/sex-matched healthy subjects in acute phase (72 h from vertigo onset) and at 2 weeks of follow-up. RESULTS: During acute phase, patients showed decreased blood pressure response during cold hand test (p < 0.05). Upright stance induced deficient decrease of the respiratory component of heart rate variability (p < 0.05) with lack of increase in low frequency/high frequency (LF/HF) ratio. At 2 weeks of follow-up, these abnormalities improved. CONCLUSIONS: Results suggest that acute vestibular lesions can interfere with cardiovascular autonomic responses in humans. This may reflect disruption of normal vestibulo-autonomic reflexes.

Adult↗

PubMedDate not supplied

[Is there a malignant neurocardiogenic syncope?].

There is a subset of patients with neurocardiogenic syncope among whom syncopal recurrences are frequent and without prodromic symptoms, or have a traumatic outcome. For this subgroup the term "malignant neurocardiogenic syncope" has been proposed. Frequently, these patients suffer from syncopes that are accompanied by profound bradycardia and prolonged asystole (more than 5 seconds). Although in the literature the term malignant is used as equal to syncope with prolonged asystole, this practice could lead to prognostic and therapeutic errors. The present article describes its clinical features, the usefulness of head-up tilt test for its therapeutic evaluation, and the wide variety of treatments that have been proposed including beta-adrenergic blockade, DDD pacemakers, and repeated tilt training program.

Humans↗

PubMedDate not supplied

[Effects of air pollution on human health and their importance in Mexico City].

The impact of air pollution on human health is a complicated problem. In this review, we describe the main health effects of exposure to ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide, lead and particulate matter. Geographical characteristics of the metropolitan area of Mexico City that favor pollutant persistence with adverse effects on the population are described; the use of the Indice Metropolitano de la Calidad del Aire (IMECA), current norms, and present programs to diminish this problem are discussed. Evidence shows that through these actions, air quality has improved. However, some pollutants such as ozone and particulate matter, still exceed the standard. To further improve air quality in the city, existing programs should continue and multidisciplinary research, both basic and applied, is required.

Air Pollutants↗

PubMedDate not supplied

[ Segmental ostial ablation to interrupt electrical conduction in a single pulmonary vein for the prevention of idiopathic paroxysmal atrial fibrillation].

Several studies have shown the role of focal trigers in the pulmonary veins initiating episodes of atrial fibrillation. Radiofrequency catheter ablation of this foci is a curative therapy for paroxysmal atrial fibrillation. We report a case of idiopathic paroxysmal atrial fibrillation triggered by abnormal electrical activity in a single pulmonary vein. Mapping was performed during sinus rhythm with a 4F decapolar catheter (Spiral Supreme, Daig, St. Jude Medical) positioned near the ostium by a transseptal approach. Pulmonary vein potentials were only identified in the left superior pulmonary vein. Segmental ostial ablation (30 W) performed during left atrial pacing resulted in complete cesation of conduction in the pulmonary vein. There were no complications. The clinical response (suppression of the paroxysms of atrial fibrillation in a 9-month follow-up) observed in this patient imply that atrial fibrillation was triggered by this pulmonary vein. This case report illustrates several aspects of catheter-based ablation of pulmonary vein foci for the treatment of paroxysmal atrial fibrillation and demonstrates its efficacy.

Adult↗