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Biomedical subjects

M F Márquez

Publications and source records attributed to M F Márquez.

13 recordsLinked to original sources
PubMed2005

Cerebral blood flow during supine rest and the first minute of head-up tilt in patients with orthostatic intolerance.

AIM: To assess the cerebral blood flow velocity during the first minute of head-up tilt in patients with postural tachycardia syndrome (POTS) or neurally-mediated reflex syncope compared with patients with dizziness. METHODS: We evaluated 120 patients selected from 470 patients who underwent head-up tilt testing: 40 with POTS, 40 with typical neurally-mediated reflex syncope and 40 who complained of dizziness with no history of loss of consciousness and a negative head-up tilt test (with and without isosorbide). Transcranial Doppler sonography of the middle cerebral artery, heart rate and brachial blood pressure were recorded during a 70 degrees head-up tilt test. RESULTS: During both baseline in supine position and the first minute of upright tilt, patients with postural tachycardia syndrome showed higher heart rate and cerebral blood flow velocity than patients with dizziness and patients with neurally-mediated reflex syncope (P < 0.05, ANOVA), but no significant difference was observed on the Gosling's pulsatility index. CONCLUSION: Patients with POTS have an autonomic dysfunction that is not triggered by upright posture but is accentuated by it.

Adult↗
PubMed2001

Anticardiolipin antibodies are not associated with rheumatic heart disease.

The aim of this study was to examine the prevalence of anticardiolipin antibodies in rheumatic valve heart disease. Serum samples of 31 consecutive patients with rheumatic heart disease and documented valve involvement, as well as six patients with acute rheumatic fever were tested for IgG anticardiolipin antibodies by a validated ELISA. No anticardiolipin antibodies were found when a cut-off point set at mean +/- 5 s.d. was applied. We can conclude that anticardiolipin antibodies are not present in rheumatic heart disease patients and, as suggested by several observations, these antibodies do not appear to have a pathogenic role in this particular disease.

Adult↗
PubMed1999

Positive head-up tilt table test in patients with the long QT syndrome.

AIMS: Syncope in patients with the long QT syndrome is commonly attributed to a ventricular arrhythmia (torsades de pointes). The susceptibility of patients with the long QT syndrome (LQTS) to neurally mediated syncope is currently unknown. METHODS AND RESULTS: Head-up tilt table testing (70 degrees) was performed in six patients with the long QT syndrome and a history of syncope. All patients had syncope with a mixed response. The RR interval was significantly decreased 2 min before the onset of syncope (980 +/- 125 ms vs 630 +/- 91 ms, P=0.003), and significantly increased during syncope (983.17 +/- 224.71; P=0.006). Non-significant changes in QT intervals were observed. Baseline QT was 513 +/- 86 ms and decreased to 450 +/- 59 ms 2 min before the onset of syncope (P=0.11). Although not statistically significant, QT intervals during syncope were longer than at 2 min before syncope (485 +/- 85 ms vs 450 +/- 59 ms; P=0.29). CONCLUSION: Our results suggest that patients with the LQTS are susceptible to neurally mediated syncope. Whether this susceptibility differs from control populations remains unresolved. From a clinical standpoint, neurocardiogenic syncope should be considered a diagnostic alternative in patients with LQTS.

Adolescent↗
PubMedDate not supplied

Differences in heart rate variability between cardioinhibitory and vasodepressor responses to head-up tilt table testing.

BACKGROUND: Patients with syncope show different responses to head-up tilt (HUT) test, which may be due to different pathophysiological mechanisms. METHODS: HUT (70 degrees) was performed in 24 patients who experienced recurrent syncope. Nine patients had a cardioinhibitory (CI) response, 7 patients had a vasodepressor (VD) response, and 8 patients had a mixed (MX) response. Heart rate variability was analyzed at 60-sec periods during HUT. RESULTS: Total spectrum (TS) was greater at rest and 1 min after syncope in the CI and MX groups as compared to the VD group. Low frequency spectrum (LF) was significantly greater during rest and the first minute after syncope in the CI groups as compared with the VD group. After the rest period, the CI and MX groups showed more elevated high frequency spectrum (HF) values than the VD group (p < 0.01). One minute after syncope, the HF increased in the CI and MX groups but not in the VD group (p < 0.01). The VD group showed higher LF/HF ratio from the beginning of rest (3.9 +/- 4.1) as compared to the CI and MX groups (p < 0.01). This difference was most significant 2 min before syncope occurred. The CI and MX groups showed greater pNN50 and rMSSD as compared to the VD group. CONCLUSIONS: Our results suggest that vagal tone is higher in subjects showing cardioinhibitory and mixed responses to HUT. In contrast, patients with a vasodepressor response showed predominantly sympathetic activity. These findings suggest that there are different pathophysiological mechanisms underlying syncope.

Adolescent↗
PubMedDate not supplied

Repeatability of heart rate variability during simple cardiovascular reflex tests on healthy subjects.

BACKGROUND: Our purpose was to determine the repeatability, after 2 weeks, of frequency domain measures of heart rate variability (HRV) during simple cardiovascular reflex tests. METHODS: Twenty healthy volunteers aged 29.3 +/- 2.5 years were assessed twice (at weeks 0 and 2). Continuous electrocardiogram and minute-to-minute blood pressure were recorded during spontaneous and metronome-paced breathing (0.2 Hz). Under paced breathing, two tests were performed: 1) active change of posture: 5 min supine position, 5 min seated upright, and 5 min standing up, and 2) cold pressor test: the right hand was immersed in cold water (5 degrees C) for 2 min. RESULTS: Paced breathing elicited a significant increase of the high-frequency (HF) component of HRV. This effect was repeatable on 95% of the subjects. Active change of posture induced a significant increase of the heart rate with an increase of the low-frequency/high-frequency ratio of HRV. Although repeatability was better for the response to being seated upright than for the response to being standing up, it was always higher than 90%. The cold pressor test induced a significant increase of the heart rate and blood pressure, but with variable changes on the HRV measurements (either a decrease or an increase). Repeatability of responses was evident for 95-100% of the subjects. Although repeatability of HRV measurements in the same subject during the tests was higher than 95%, coefficients of repeatability reflected large differences among the subjects. CONCLUSIONS: The results suggest that it is not advisable to use isolated HRV changes to interpret the response to simple cardiovascular reflex tests in groups of healthy subjects.

Cardiovascular Physiological Phenomena↗
PubMedDate not supplied

Orthostatic hypotension, 2001.

Upright posture requires rapid and effective circulatory and neurologic compensations to maintain blood pressure and consciousness. Although it has been recognized over the past 100 years or more that the act of standing may cause hypotension in patients with autonomic dysfunction, only recently several of the pathophysiologic mechanisms resulting in orthostatic intolerance have been discovered. In patients with orthostatic hypotension, failure of reflex vasoconstriction causes pooling of blood in the legs during standing. Not everyone with a postural blood pressure drop requires treatment, nor does everyone with posturally induced symptoms have orthostatic hypotension. This review will discuss current knowledge of a broad, heterogeneous group of disturbances in the autonomic nervous system, each of which is manifested by hypotension, orthostatic intolerance, and often syncope.

Humans↗
PubMedDate not supplied

[Myocardial injury caused by reperfusion].

Arterial coronary occlusion produces ischaemic changes, and alter the aerobic metabolism, creatinephosphate depletion and accumulation of anoxic metabolites in the ischaemic tissue, with an alteration in the calcium regulation. With the recovery of the blood flow, the myocardial ischaemic injury and infarct zone are diminished, leading to an improvement of survival. The adverse effect induced by the reperfusion of ischaemic cells with the production of free radicals and dearrangements in the glucose metabolism, fatty acids and intracellular calcium flow as well, has been proven. There are 4 kinds of reperfusion damage: stunned myocardium, reperfusion arrhythmia, no-reflow phenomena, and cellular death, all of them with a particular physiopathology. Nowadays, there are too many paraclinics in order to reach a diagnosis, and perhaps the only available treatment is still under research. This field has great expectancy in the future. In this article, some of the contemporary concepts are reviewed.

Humans↗