Increased plasma catecholamine levels in patients with symptomatic mitral valve prolapse

Plasma catecholamines in patients undergoing invasive cardiopulmonary exercise test for exercise intolerance

BACKGROUND

Invasive cardiopulmonary exercise testing (iCPET) combines traditional cardiopulmonary exercise testing with invasive hemodynamic measurements to assess exercise intolerance, which can be caused by preload insufficiency (PI), characterized by low ventricular filling pressures and reduced cardiac output during exertion. We hypothesize that plasma catecholamine levels at rest and during exercise correlate with hemodynamic parameters in PI.

METHODS

We included adult patients who underwent iCPET for exercise intolerance and had plasma catecholamines measured at rest and peak exercise.

RESULTS

Among 84 patients, PI was identified in 57 (67.8 %). Compared to patients without PI, those with PI were younger [median (IQR) 37 (28, 46) vs 47 (39,55) years, p = 0.005] and had lower workload at peak exercise [81 (66, 96) vs 95 (83.5, 110.50) Watts, p = 0.006]. Patients with PI had higher heart rates at rest and peak exercise [87 (78, 97) vs 79 (74, 87) bpm, p = 0.04; and 167 (154, 183) vs 156 (136, 168) bpm, p = 0.01, respectively]. In all patients, epinephrine and norepinephrine at peak exercise directly correlated with peak workload (r:0.41, p < 0.001 and r:0.47, p < 0.001, respectively). Resting epinephrine was higher in patients with PI [136 (60, 210) vs 77 (41, 110) pg/mL, p = 0.02]. There was no significant difference in the change in catecholamines from rest to peak exercise between patients with or without PI.

CONCLUSION

PI patients exhibited elevated heart rate and epinephrine at rest, indicating increased sympathetic activity. We did not find strong associations between catecholamines and cardiac filling pressures, suggesting that catecholamine levels are predominantly influenced by peak workload.

Are children with mitral valve prolapse more anxious?

Background

Mitral valve prolapse (MVP) is a common valvular disease in children. Symptoms in children with MVP are not explained by the severity of mitral regurgitation alone. Hence, we sought to correlate symptom status with the incidence of anxiety disorder in this population.

Materials and Methods

Groups were as follows: (a) MVP; n = 115; mean age: 13.5 ± 3.06 years and (b) control; n = 53; mean age: 15.1 ± 13.2. The Screen for Child Anxiety-Related Emotional Disorders (SCAREDs) scale was filled by all participants. The SCARED scores of 25 and above determined a warning for anxiety disorders.

Results

The mean SCARED scale values of MVP and control groups were 29.2 ± 13.08 and 24.9 ± 14.17, respectively (P = 0.065). Although the SCARED scale score was higher among the MVP patients, no significant difference was found between the groups in terms of the mean SCARED score, or the number of participants with a score of 25 or more. While girls with MVP had higher anxiety scores compared to boys with the disorder, there was no difference with respect to SCARED scores in children with MVP and the general population when analyzed separately by gender. Moreover, the SCARED scale score was significantly higher in symptomatic MVP patients than in asymptomatic cases.

Conclusion

Children with MVP did not have higher anxiety scores compared to those without the syndrome. However, MVP patients with higher anxiety scores may benefit from a psychiatric assessment since higher scores correlate with symptoms.

Sympathetic nervous system and cardiovascular risk in mitral valve prolapse

Mitral valve prolapse (MVP) represents a frequent cardiovascular condition associated with increased cardiovascular risk, which may have progressive course and become malignant. Dysregulation of autonomic nervous system - especially sympathetic overdrive – is one of the factors considered to play a key role in its aetiology and development. There is a growing evidence of a large impact of sympathetic system on the development of MVP. Exaggerated sympathetic activity may lead to morphologic changes in valves tissue such as thickening and redundancy. Nowadays, few investigative methods are known for evaluation of the regulatory state of sympathetic nervous system, which could be, theoretically, used to identify the subjects with sympathetic overactivity associated with an increased cardiovascular risk. Electrodermal activity or blood pressure variability represent promising non-invasive methods for evaluation of the regulatory outputs of sympathetic nervous system. There is a possibility to extend a set of investigative methods in MVP and include the monitoring of sympathetic activity in the assessment of cardiovascular risk. This article summarizes knowledge about pathogenesis, diagnostic and therapeutical approaches of MVP, and brings some novel insights on the parameters of autonomic nervous regulation, which haven’t yet been used in cardiovascular risk assessment in MVP.

Prolonged Tp-e Interval and Tp-e/QT Ratio in Children with Mitral Valve Prolapse

Although it is considered to be a benign condition, previous studies have shown that a subset of patients with mitral valve prolapse (MVP) may be at risk of ventricular arrhythmia and sudden cardiac death (SCD). Previous studies have suggested that the interval between the peak and the end of the T wave (Tp-e) can be used as a marker for the transmural dispersion of repolarization. Increased Tp-e interval and Tp-e/QT ratio are associated with ventricular arrhythmias and SCD. The aim of this study was to assess alterations in ventricular repolarization by using the Tp-e interval and Tp-e/QT ratio in children with MVP and to investigate their relationships with the degree of valvular regurgitation. This study prospectively investigated 110 children with MVP and 107 age- and sex-matched healthy control subjects. Tp-e interval, Tp-e/QT ratio, and QT and QTc dispersions were measured from a 12-lead electrocardiogram and compared between groups. QT and QTc dispersions, Tp-e interval, and Tp-e/QTc ratio were found to be significantly higher in patients with MVP. A positive correlation was found between Tp-e/QTc ratio and increase in the degree of mitral regurgitation (MR) (p < 0.05; r = 0.2). However, the degree of MR was not associated with QT, QTc, or Tp-e intervals; QT, QTc, or Tp-e dispersions; or Tp-e/QT ratio (all p values >0.05). Individuals with MVP may be more prone to ventricular arrhythmias due to prolonged QTd, QTcd, and Tp-e interval and increased Tp-e/QT and Tp-e/QTc ratios. Therefore, due to their longer life expectancy, children with MVP should be followed up on regarding life-threatening arrhythmias.

Posture and Gender Differentially Affect Heart Rate Variability of Symptomatic Mitral Valve Prolapse and Normal Adults

BACKGROUND

Heart rate variability (HRV) has been shown to be a useful measure of autonomic activity in healthy and mitral valve prolapsed (MVP) subjects. However, the effects of posture and gender on HRV in symptomatic MVP and normal adults had not been elucidated in Taiwan.

METHODS

A total of 118 MVP patients (7 males, 39 ± 7 years old; and 111 females, 42 ± 13 years old) and 148 healthy control (54 males, 28 ± 4 years old; and 94 females, 26 ± 6 years old) were investigated. The diagnosis of MVP was confirmed by cross-sectional echocardiography. A locally developed Taiwanese machine was used to record the HRV parameters for MVP and control groups in three stationary positions. Thereafter, the HRV time-domain parameters, and the frequency-domain parameters derived from fast Fourier transform or autoregressive methods were analyzed.

RESULTS

The MVP group showed a decrease in time domain parameters and obtunded postural effects on frequency domain parameters moreso than the control group. Though the parasympathetic tone was dominant in female (higher RMSSD, nHF and lower nLF vs. male), the sympathetic outflow was higher in MVP female (lower SDNN, NN50 and higher nLF vs. normal female). While the parasympathetic activity was lower in male, sympathetic outflow was dominant in MVP male (lower nHF and higher nLF vs. normal male).

CONCLUSIONS

Both MVP female and male subjects had elevated levels of sympathetic outflow. The obtunded postural effects on frequency domain measures testified to the autonomic dysregulation of MVP subjects.

Floppy mitral valve/mitral valve prolapse syndrome: Beta-adrenergic receptor polymorphism may contribute to the pathogenesis of symptoms

BACKGROUND

Certain patients with floppy mitral valve (FMV)/mitral valve prolapse (MVP) may have symptoms that cannot be explained on the severity of mitral valvular regurgitation (MVR) alone; hypersensitivity to adrenergic stimulation has been suggested in this group defined as the FMV/MVP syndrome.

METHODS

Ninety-eight patients (75 men, 23 women) with mitral valve surgery for FMV/MVP were studied. Of those 41 (42%) had symptoms consistent with FMV/MVP syndrome [29 men (39%), 12 women (52%)]; median age of symptom onset was 30 years (range 10-63 years) and median duration of symptoms prior to valve surgery was 16 years (range 3-50 years). Ninety-nine individuals (70 men, 29 women) without clinical evidence of any disease were used as controls. Genotyping of β1 and β2 adrenergic receptors was performed.

RESULTS

β-Adrenergic receptor genotypes (β1 and β2) were similar between control and overall FMV/MVP patients. Subgroup analysis of patients, however, demonstrated that the genotype C/C at position 1165 resulting in 389 Arg/Arg of the β1 receptor was more frequent in women compared to those without FMV/MVP syndrome and to normal control women (p<0.025). This polymorphism may be related to hypersensitivity to adrenergic stimulation as reported previously in these patients.

CONCLUSION

This study shows a large proportion of patients with FMV/MVP, predominantly women, had symptoms consistent with the FMV/MVP syndrome for many years prior to the development of significant MVR, and thus symptoms cannot be attributed to the severity of MVR alone. Further, women with FMV/MVP syndrome, symptoms at least partially may be related to β1-adrenergic receptor polymorphism, which has been shown previously to be associated with a hyperresponse to adrenergic stimulation.

Age- and Gender-Normalized Coronary Incidence and Mortality Risks in Primary and Secondary Prevention

Epidemiologic differences in ischemic heart disease incidence between women and men remain largely unexplained. The reasons of women’s “protection” against coronary artery disease (CAD) are not still clear. However, there are subsets more likely to die of a first myocardial infarction. The purpose of this review is to underline different treatment strategies between genders and describe the role of classical and novel factors defined to evaluate CAD risk and mortality, aimed at assessing applicability and relevance for primary and secondary prevention. Women and men present different age-related risk patterns: it should be important to understand whether standard factors may index CAD risk, including mortality, in different ways and/or whether specific factors might be targeted gender-wise. Take home messages include: HDL-cholesterol levels, higher in pre-menopausal women than in men, are more strictly related to CAD. The same is true for high triglycerides and Lp(a). HDL-cholesterol levels are inversely related to incidence and mortality. In primary prevention the role of statins is not completely ascertained in women although in secondary prevention these agents are equally effective in both genders. Weight and glycemic control are effective to reduce cardiovascular disease (CVD) mortality in women from middle to older age. Blood pressure is strongly and directly related to CVD mortality, from middle to older age, particularly in diabetic and over weighted women. Kidney dysfunction, defined using UAE and eGFR predicts primary CVD incidence and risk in both genders. In secondary prediction, kidney dysfunction predicts sudden death in women in conjunction with left ventricular ejection fraction evaluation. Serum uric acid does not differentiate gender-related CVD incidences, although it increases with age. Age-related differences between genders have been related to loss of ovarian function traditionally and to lower iron stores more recently. QT interval, physiologically longer in women than men, may be an index of arrhythmic risk in patients with mitral valve prolapse and increased circulating levels of catecholamines. However, there are no large population-based studies to assess this. In conjunction with novel parameters, such as inflammatory markers and reproductive hormones, classical risk score in women may be implemented in the future.

P-wave dispersion and heart rate variability in children with mitral valve prolapse

Previous studies have reported that patients with mitral valve prolapse (MVP) may display autonomic dysfunction. Measurement of heart rate variability (HRV) and P-wave dispersion (PWD) may provide insights into the functional state of the autonomic nervous system. Heart rate variability (HRV) has been used as a noninvasive marker of autonomic activity. However, to the authors' knowledge, PWD has not been studied in the context of MVP. This study aimed to examine HRV and PWD in patients with MVP and to determine whether differences exist between symptomatic and asymptomatic patients. The study population consisted of 54 healthy children (17 boys and 37 girls) ages 6-18 years and 76 patients with MVP (20 boys and 56 girls) ages 6-18 years. The duration and dispersion of the P-wave were measured by surface 12-lead electrocardiograms (ECGs). Heart rate variability was quantified using both time-domain and frequency-domain analyses of Holter ECGs. The minimum duration of the P-wave was significantly lower in the MVP patients (42.4 ± 10.0 ms) than in the control subjects (54.4 ± 12.8 ms) (p < 0.01), and the PWD was significantly increased in the MVP group (42.7 ± 10.8 ms) compared with the control subjects (31.8 ± 10.9 ms) (p < 0.01). However, no significant differences were found between the symptomatic and asymptomatic patients. In addition, the HRV parameters were not statistically different between the two groups. In conclusion, although HRV parameters were not significantly different between the MVP and control groups, the findings show that PWD was increased for the children with MVP. However, no relationship could be established between PWD and clinical symptoms.

ST-Segment Depression in Hyperventilation Indicates a False Positive Exercise Test in Patients with Mitral Valve Prolapse

Objectives. Mitral valve prolapse (MVP) is a known cause for false positive exercise test (ET). The purpose of this study was to establish additional electrocardiographic criteria to distinguish the false positive exercise results in patients with MVP. Methods. We studied 218 consecutive patients (53 ± 6 years, 103 males) with MVP (according to echocardiographic study), and positive treadmill ET was performed due to multiple cardiovascular risk factors or angina-like symptoms. A coronary angiography was performed to detect coronary artery disease (CAD). Results. From 218 patients, 90 (group A) presented with normal coronary arteries according to the angiography (false positive ET) while the rest 128 (group B) presented with CAD. ST-segment depression in hyperventilation phase was present in 54 patients of group A (60%) while only in 14 patients of group B (11%), P < .05. Conclusions. Presence of ST-segment depression in hyperventilation phase favors a false positive ET in patients with MVP.

Panic disorder, social anxiety disorder, and a possible medical syndrome previously linked to chromosome 13

BACKGROUND

Several studies have identified increased medical problems among individuals with panic disorder (PD). We previously found that specific conditions--interstitial cystitis (IC), mitral valve prolapse (MVP), migraines, and thyroid disorders--aggregated non-randomly among panic families (we called this the "PD syndrome") and that families with and without the syndrome were genetically distinguishable on chromosome 13. We present data from a new case-control study that replicates and extends the syndrome phenotype clinically.

METHODS

Probands with a definite diagnosis and family history of PD (n=219), social anxiety disorder (SAD; n=199), or both (n=173) and 102 control subjects with no personal/family history of anxiety were interviewed with the SADS-LA diagnostic instrument. Medical history was obtained via medical checklist and the family history screen; IC symptoms were assessed with criteria developed by the National Institute for Diabetes and Digestive and Kidney Diseases. Subjects and interviewers were unaware of the syndrome hypothesis; final best-estimate diagnoses were blind to syndrome data.

RESULTS

Probands with PD or SAD, as compared with control subjects, were five or more times as likely to report IC symptoms and twice as likely to report MVP and migraines (other genitourinary and cardiovascular problems were not elevated). First-degree relatives of probands with PD or SAD were also at increased risk for IC, MVP, thyroid problems, and headaches, regardless of whether the proband reported the same condition.

CONCLUSIONS

These findings are consistent with previous data supporting a PD syndrome and further suggest that this syndrome might include other anxiety disorders well.

QT dispersion and diastolic functions in differential diagnosis of primary mitral valve prolapse and rheumatic mitral valve prolapse

There is no specific criteria established to guide physicians in the differential diagnosis of primary mitral valve prolapse (MVP) and rheumatic MVP. Previous studies suggested that history and pathology of mitral valve could be helpful in differential diagnosis of MVP. The aim of this study was to evaluate the value of QT interval, QT dispersion, and diastolic function in differential diagnosis of MVP. We examined electrocardiographies and echocardiographies of 24 primary MVP patients, 20 rheumatic MVP patients, and 21 healthy subjects. MVP was defined as superior displacement of the mitral leaflets more than 2 mm into the left atrium during systole. QT dispersion was significantly higher in primary MVP patients (71 +/- 13.5 ms, p < 0.01). Maximum QT dispersion value in rheumatic MVP patients was 55 ms. E and A velocity values which show ventricular early and late diastolic filling, were lower in primary MVP patients (p < 0.01). There was no difference in the heart rate corrected QT interval values between the primary MVP patients (397 +/- 28.1), rheumatic MVP patients (403 +/- 23.8) and healthy children (404 +/- 15.8; p > 0.05). Our findings may indicate that QT dispersion can be used as a parameter for differential diagnosis of primary MVP and rheumatic MVP. Further studies are needed to identify a cut-off point of QT dispersion.

Postural orthostatic tachycardia syndrome

Postural orthostatic tachycardia syndrome (POTS) is an autonomic disturbance which has become better understood in recent years. It is now thought to encompass a group of disorders that have similar clinical features, such as orthostatic intolerance, but individual distinguishing parameters--for example, blood pressure and pulse rate. The clinical picture, diagnosis, and management of POTS are discussed.

Effect of metoprolol on heart rate variability in symptomatic patients with mitral valve prolapse

Metoprolol is widely used to eliminate symptoms in patients with mitral valve prolapse (MVP), a condition associated with enhanced sympathetic tone. In this study, effects of metoprolol on heart rate variability (HRV) indices were investigated in symptomatic patients with MVP. Thirty-nine symptomatic patients with MVP (26 women, mean age 26 +/- 7 years) and 16 age- and gender-matched controls were studied. After a baseline 24-hour Holter evaluation in all subjects, patients with MVP were started on metoprolol succinate therapy at a dose of 25 to 100 mg/d, and Holter analysis was repeated at the end of 3 months of metoprolol therapy. At the basal evaluation, all time-domain HRV indices with the exception of proportion of adjacent RR intervals differing by >50 ms in the 24-hour recording were significantly lower in patients with MVP than controls (SD of all normal-to-normal [NN] intervals, p = 0.013; SD of average NN intervals calculated during 5-minute periods of the entire recording, p = 0.03; triangular index, p = 0.025; and square root of mean squared differences in successive NN intervals, p = 0.026). After metoprolol treatment, all HRV indices significantly improved compared with baseline (SD of all NN intervals, p = 0.028; SD of average NN intervals calculated during 5-minute periods of the entire recording, p = 0.043; triangular index, p = 0.004; square root of the mean squared differences in successive NN intervals, p = 0.021; and proportion of adjacent RR intervals differing by >50 ms in the 24-hour recording, p = 0.014), and HRV indices after metoprolol treatment were similar to those of the control group (p >0.05). In conclusion, metoprolol significantly improved impaired HRV parameters in symptomatic patients with MVP.

Heart rate turbulence and heart rate variability in patients with mitral valve prolapse

AIMS

Heart rate turbulence (HRT) and heart rate variability (HRV) have been shown to be independent and powerful predictors of mortality in a specific group of cardiac patients. However, the predictive values of HRV alone is modest and information on HRV in patients with mitral valve prolapse (MVP) has so far been conflicting. In addition, no studies have previously evaluated HRT in patients with MVP. To define better the effects of MVP on cardiac autonomic function, we assessed HRT and time-domain parameters of HRV in patients with MVP.

METHODS AND RESULTS

Fifty patients with MVP and 70 controls without MVP were investigated. The diagnosis of MVP was confirmed by cross-sectional echocardiography in the parasternal long-axis view and apical 4-chamber view. The HRV and turbulence analysis were assessed from a 24-hour Holter recording. When HRT parameters were compared, the values of the HRT onset and slope were significantly lower in MVP patients than in the controls group (-0.109+/-0.207 vs. -0.289+/-0.170%, P=0.001 and 8.6+/-7.2 vs. 11.5+/-7.4 ms/RRI, P=0.043, respectively) and the number of patients who had abnormal HRT onset was significantly higher in the MVP group than in controls (15 vs. 8, P=0.011). In addition, HRV parameters were not statistically different between the two groups.

CONCLUSION

Although we found that the decrease in HRV parameters was not significantly different between MVP patients and controls, HRT variables (especially HRT onset) were significantly lower in MVP patients. Therefore, in our opinion, HRT is an attractive, easily applicable, and better way of non-invasive risk prediction compared with another non-invasive risk predictor, HRV.

Mitral valve prolapse

Mitral valve prolapse is a common valvular abnormality that is the most common cause of severe non-ischaemic mitral regurgitation in the USA. The overall prognosis of patients with mitral valve prolapse is excellent, but a small subset will develop serious complications, including infective endocarditis, sudden cardiac death, and severe mitral regurgitation. We present a comprehensive review of mitral valve prolapse, examining normal mitral anatomy, the clinical and echocardiographic features of mitral valve prolapse, and the pathophysiology and genetics of the disorder. We discuss the contemporary management of both asymptomatic and symptomatic prolapse, with particular attention to the timing and technique of surgical repair. We conclude that echocardiography is the method of choice for diagnosing mitral valve prolapse, that clinical and echocardiographic features can predict which patients with prolapse are at highest risk for complications, and that mitral valve repair is the treatment of choice for symptomatic prolapse.

The neuropathic postural tachycardia syndrome

BACKGROUND

The postural tachycardia syndrome is a common disorder that is characterized by chronic orthostatic symptoms and a dramatic increase in heart rate on standing, but that does not involve orthostatic hypotension. Several lines of evidence indicate that this disorder may result from sympathetic denervation of the legs.

METHODS

We measured norepinephrine spillover (the rate of entry of norepinephrine into the venous circulation) in the arms and legs both before and in response to exposure to three stimuli (the cold pressor test, sodium nitroprusside infusion, and tyramine infusion) in 10 patients with the postural tachycardia syndrome and in 8 age- and sex-matched normal subjects.

RESULTS

At base line, the mean (+/-SD) plasma norepinephrine concentration in the femoral vein was lower in the patients with the postural tachycardia syndrome than in the normal subjects (135+/-30 vs. 215+/-55 pg per milliliter [0.80+/-0.18 vs. 1.27+/-0.32 nmol per liter], P=0.001). Norepinephrine spillover in the arms increased to a similar extent in the two groups in response to each of the three stimuli, but the increases in the legs were smaller in the patients with the postural tachycardia syndrome than in the normal subjects (0.001+/-0.09 vs. 0.12+/-0.12 ng per minute per deciliter of tissue [0.006+/-0.53 vs. 0.71+/-0.71 nmol per minute per deciliter] with the cold pressor test, P=0.02; 0.02+/-0.07 vs. 0.23+/-0.17 ng per minute per deciliter [0.12+/-0.41 vs. 1.36+/-1.00 nmol per minute per deciliter] with nitroprusside infusion, P=0.01; and 0.008+/-0.09 vs. 0.19+/-0.25 ng per minute per deciliter [0.05+/-0.53 vs. 1.12+/-1.47 nmol per minute per deciliter] with tyramine infusion, P=0.04).

CONCLUSIONS

The neuropathic postural tachycardia syndrome results from partial sympathetic denervation, especially in the legs.

Heart rate variability of children with mitral valve prolapse

Studies have indicated that adult patients with mitral valve prolapse (MVP) may have autonomic dysfunction. The purpose of this study was to evaluate heart rate variability (HRV) in children with MVP. Sixty-seven children with MVP (ages 6 to 18 years; 30 boys and 37 girls) were consecutively studied and subdivided into those with or without symptoms. Thirty-seven normal age-matched children (17 boys and 20 girls) were studied as controls. The patients were further divided into 4 age subgroups. HRV was measured using a 24-hour Holter electrocardiogram (ECG) system (Laser SXP Holter Analysis System, Marquette Electronics, Milwaukee, WI). The ECGs were analyzed in both time domain and frequency domain (spectral analysis). Symptomatic and asymptomatic children with MVP were combined for analysis because they were not significantly different in terms of their HRV. All time-domain indices, with the exception of SDANN (SD of the mean of RR intervals in all 5-minute segments of the 24-hour ECG), were significantly lower in children with MVP than in controls. Children with MVP showed significantly lower spectral power of the high frequency (HF) and low frequency (LF) components when compared with controls. The ratio of LF to HF (LF/HF) was significantly higher in children with MVP. Similar differences were observed in the 4 age subgroups. Sex differences in HRV were observed when girls had lower HRV compared with boys. Lower time-domain and frequency-domain indices of HRV in children with MVP are suggestive of decreased parasympathetic activity and a shift in sympathovagal balance. Various factors including differences in heart rate may contribute to sex differences in HRV.

Chronic orthostatic intolerance: a disorder with discordant cardiac and vascular sympathetic control

BACKGROUND

Chronic orthostatic intolerance (COI) is a debilitating autonomic condition in young adults. Its neurohumoral and hemodynamic profiles suggest possible alterations of postural sympathetic function and of baroreflex control of heart rate (HR).

METHODS AND RESULTS

In 16 COI patients and 16 healthy volunteers, intra-arterial blood pressure (BP), ECG, central venous pressure (CVP), and muscle sympathetic nerve activity (MSNA) were recorded at rest and during 75 degrees tilt. Spectral analysis of RR interval and systolic arterial pressure (SAP) variabilities provided indices of sympathovagal modulation of the sinoatrial node (ratio of low-frequency to high-frequency components, LF/HF) and of sympathetic vasomotor control (LFSAP). Baroreflex mechanisms were assessed (1) by the slope of the regression line obtained from changes of RR interval and MSNA evoked by pharmacologically induced alterations in BP and (2) by the index alpha, obtained from cross-spectral analysis of RR and SAP variabilities. At rest, HR, MSNA, LF/HF, and LFSAP were higher in COI patients, whereas BP and CVP were similar in the two groups. During tilt, BP did not change and CVP fell by the same extent in the 2 groups; the increase of HR and LF/HF was more pronounced in COI patients. Conversely, the increase of MSNA was lower in COI than in control subjects. Baroreflex sensitivity was similar in COI and control subjects at rest; tilt reduced alpha similarly in both groups.

CONCLUSIONS

COI is characterized by an overall enhancement of noradrenergic tone at rest and by a blunted postganglionic sympathetic response to standing, with a compensatory cardiac sympathetic overactivity. Baroreflex mechanisms maintain their functional responsiveness. These data suggest that in COI, the functional distribution of central sympathetic tone to the heart and vasculature is abnormal.

Clinical symptoms of mitral valve prolapse are related to hypomagnesemia and attenuated by magnesium supplementation

Mitral valve prolapse syndrome (MVP) is a frequent disorder characterized by a number of complaints which lessen the quality of life. The pathogenesis of MVP symptoms has not been fully elucidated. Hyperadrenergic activity and magnesium deficiency have been suggested. This study was designed to verify the concept that heavily symptomatic MVP is accompanied by hypomagnesemia and to elucidate whether magnesium supplementation alleviates the symptoms and influences adrenergic activity. We assessed serum magnesium in 141 subjects with heavily symptomatic primary MVP and in 40 healthy controls. Decreased serum magnesium was found in 60% of patients and in 5% of controls (p <0.0001). Patients with low serum magnesium were subjected to magnesium or placebo supplementation in a double-blind, crossover fashion. Typical symptoms of MVP (n = 13), intensity of anxiety, and daily excretion of catecholamines were determined. After 5 weeks, the mean number of symptoms per patient decreased from 10.4 +/- 2.1 to 5.6 +/- 2.5 (p <0.0001), and a significant reduction in weakness, chest pain, dyspnea, palpitations, and anxiety was observed. Increased noradrenaline excretion before and after magnesium was seen in 63% and 17% of patients, respectively (p <0.01). Mean daily excretion of noradrenaline and adrenaline was significantly diminished after magnesium. It is concluded that many patients with heavily symptomatic MVP have low serum magnesium, and supplementation of this ion leads to improvement in most symptoms along with a decrease in catecholamine excretion.

Is there increased sympathetic activity in patients with mitral valve prolapse?

The aim of this study was to investigate autonomic nervous system tone in patients with mitral valve prolapse (MVP). Heart rate variability (HRV) was assessed from 24-hour ambulatory Holter recordings in 28 patients with primary MVP and in 28 age and sex matched normal control subjects in a drug-free state. Sixteen of the MVP patients were symptomatic and 12 asymptomatic. Spectral HRV was calculated in terms of low (LF: 0.06-0.15 Hz) and high (HF: 0.15-0.40 Hz) frequency components using fast Fourier transform analysis, and the ratio LF/HF was calculated. Spectral analysis of HRV showed that the MVP patients, taken as a single group, had lower HF and LF and a higher LF/HF ratio than the controls. No significant difference in HRV was found between the 16 symptomatic and the 12 asymptomatic patients, but the symptomatic patients had a significantly higher LF/HF ratio than the controls. Our observations suggest that, during normal daily activities, patients with MVP experience a significant deviation in autonomic nervous system tone with predominance of the sympathetic branch. This predominance is more marked in symptomatic patients.

Autonomic control of cardiovascular function: clinical evaluation in health and disease

The high- and low-pressure baroreceptor reflexes are integral to the control of blood pressure by the autonomic nervous system. Tests of the integrity of these baroreflexes make it possible to identify the site of autonomic dysfunction in patients with orthostatic hypotension. Clinical characteristics and typical results of autonomic testing in patients with autonomic failure, with carotid sinus hypersensitivity, and with hyperadrenergic autonomic dysfunction are described in this review.

The phenomenon of dysautonomia and mitral valve prolapse

In recent years research has shown that subsets of patients with mitral valve prolapse also have associated autonomic or neuroendocrine dysfunction that can result in a number of related symptoms, including fatigue, palpitations, chest pain, exercise intolerance, dyspnea, dizziness, headache, sleep disorders, gastrointestinal disturbances, cold extremities, and panic attacks. These patients have been classified as having mitral valve prolapse syndrome. This article discusses the pathogenesis and management of mitral valve prolapse syndrome and serves to make clinicians aware of newer developments in the study of autonomic function and dysfunction.

[Cardiovascular pathology and panic disorder]

The relationship between anxiety and cardiovascular function and symptoms has long been of interest, culminating in the recent emphasis on the modulation of cardiovascular response in patients with panic disorder. The relationship between panic disorder and mitral valve prolapse remains controversial. Panic disorder appears to be significantly associated with increased incidence of cardiovascular morbidity. The detection and treatment of panic disorder in patients with cardiovascular risk or diseases could have an important impact on prognosis and quality of life of the patients.

Assessment of cardiac adrenergic supply in mitral valve prolapse using m-[123I]iodobenzylguanidine scintigraphy

Presynaptic as well as postsynaptic adrenergic regulation abnormalities are reported in symptomatic patients with mitral valve prolapse. This study was undertaken to evaluate presynaptic sympathetic supply by m-[123I]iodobenzylguanidine scintigraphy in 17 preselected patients with mitral valve prolapse and symptoms suggestive of hyperadrenergic dysautonomia as compared to normal scintigraphic findings. Mitral valve prolapse was echocardiographically proven within the left parasternal long axis view. Percentual activity of m-[123I]iodobenzylguanidine in 33 sectors of all oblique slices along the short axis was calculated relative to the maximal uptake, set at 100%. In general, no significant differences of mean values of sectoral quantitative uptake of m-[123I]iodobenzylguanidine were detectable between patients and the control group. Only in two sectors of the basal anterolateral region P values < 0.01 were present. Thus, using m-[123I]iodobenzylguanidine scintigraphy as marker of cardiac adrenergic supply, no evidence of altered presynaptic hyperadrenergic supply was present in patients with mitral valve prolapse. These findings suggest postsynaptic regulation abnormalities to be preponderant in this condition.

Gender related differences in the cardiovascular responses to upright tilt in normal subjects

The heart rate and blood pressure responses to head-up tilt of 80 degrees was studied in 20 normal men and 21 normal women aged 20-50 years (mean age 31.1 +/- 7.1 years). The heart rate increase in females during tilt was 73% that of males, whereas the increase in diastolic pressure during tilt was 29% of males. Expressed in relation to values obtained supine, heart rate increases on average 30.3% in men as compared to 21.5% in women whereas diastolic pressure increases by 15.2% in men as compared to an increase of only 4.3% in women. The data indicates that the cardiovascular response of normal females to upright tilt differs significantly from that of normal males. This attenuated responsiveness to orthostasis in women relative to men may predispose women to postural insufficiency and may account for the predominance of symptomatic women with clinically mild dysautonomia.

Haemodynamic and neurohormonal responsiveness to different stress tests in mitral valve prolapse

In this study the blood pressure, heart rate, plasma noradrenaline and plasma adrenaline responses to various forms of sympatho-neural stress were evaluated in patients with mitral valve prolapse (MVP). Sympathetic reactivity in different subgroups of MVP were related to the degree of ventricular arrhythmia. Thirty-eight patients with mitral valve prolapse and 17 healthy controls were studied. All underwent 24-h ECG recording, 2-D echocardiography, head-up tilt to 60 degrees, pressor tests (sustained handgrip, mental arithmetic, cold pressor) and psychological assessment. The blood pressure, noradrenaline and adrenaline response to stress in patients without premature ventricular contraction were similar to those of the controls. In patients with unifocal premature ventricular contraction (PVC) less than 300/h, responses were similar to normal but were associated with higher plasma noradrenaline levels in the basal state and a diminished response to isometric stress. In patients with more than 300/h unifocal premature ventricular contraction, pairs of premature ventricular contraction, or runs of ventricular tachycardia there were lower blood pressure values in the basal state with reduced blood pressure, heart rate and plasma noradrenaline and adrenaline responses to head-up tilt and sustained handgrip, but marked increases in blood pressure, heart rate and plasma noradrenaline levels during the cold pressor test. Our data suggest different degrees of autonomic involvement in mitral valve prolapse which may be related to the various degrees of arrhythmia which seem to contribute to their symptoms.

Mitral valve prolapse, panic disorder, and chest pain

Mitral valve prolapse is a common cardiac disorder that can readily be diagnosed by characteristic auscultatory and echocardiographic criteria. Although many diseases have been associated with mitral valve prolapse, most affected individuals have the primary form of the disorder. Mitral valve prolapse is an inherited condition commonly associated with myxomatous degeneration of the mitral valve and its support structures. Complications of mitral valve prolapse, including cardiac arrhythmias, sudden death, infective endocarditis, severe mitral regurgitation (with or without chordae tendineae rupture), and cerebral ischemic events, occur infrequently considering the wide prevalence of the disorder. Panic disorder is a specific type of anxiety disorder characterized by at least three panic attacks within a 3-week period or one panic attack followed by fear of subsequent panic attacks for at least 1 month. It too is a common condition with a prevalence and age and gender distribution similar to that of mitral valve prolapse. Panic disorder and mitral valve prolapse share many nonspecific symptoms, including chest pain or discomfort, palpitations, dyspnea, effort intolerance, and pre-syncope. Chest pain is the symptom in both conditions that most commonly brings the patient to medical attention. The clinical description of chest pain in patients with mitral valve prolapse is highly variable, possibly reflecting multiple etiologies. Chest pain in panic disorder is usually characterized as atypical angina pectoris and as such bears resemblance to the chest pain commonly described by patients with mitral valve prolapse. Multiple investigative attempts to elucidate the mechanism of chest pain in both conditions have failed to identify a unifying cause. Review of the literature leaves little doubt that mitral valve prolapse and panic disorder frequently co-occur. Given the similarities in their symptomatology, a high rate of co-occurrence is, in fact, entirely predictable. There is, however, no convincing evidence of a cause-effect relationship between the two disorders, nor has a single pathophysiologic or biochemical mechanism been identified that unites these two common conditions. Until specific biologic markers for these disorders are identified, it may be impossible to do so. The lack of a proven cause-and-effect relationship between mitral valve prolapse and panic disorder and the absence of a unifying mechanism do not diminish the clinical significance of the high rate of co-occurrence between the two conditions. Primary care physicians and cardiologists frequently encounter patients with mitral valve prolapse and nonspecific symptoms with no discernible objective cause who fail to respond to beta-blockade. Panic disorder should be considered as a possible explanation for symptoms in such patients.(ABSTRACT TRUNCATED AT 400 WORDS)

Altered beta adrenergic receptor function in subjects with symptomatic mitral valve prolapse

Individuals with mitral valve prolapse (MVP) frequently show symptoms of a hyperadrenergic state. beta adrenergic receptor characteristics were compared in the lymphocytes of subjects with symptomatic MVP and control subjects during rest and exercise. At rest, the proportion of receptors binding agonist with high affinity, as determined from isoproterenol competition for (-)[125I]-iodopindolol binding sites, was greater in MVP subjects than in controls. With exercise, the proportion of high-affinity receptors in MVP subjects decreased to control levels. Isoproterenol stimulation of lymphocyte 3',5'-cyclic adenosine monophosphate (cyclic AMP) also was greater in MVP subjects than in controls at rest, but not during exercise. Plasma catecholamine concentrations in MVP subjects were normal during both rest and exercise. Unlike exercise, isoproterenol infusion elicited clinical manifestations of increased adrenergic responsiveness in MVP subjects. The beta receptor in exercised MVP subjects exhibited unusually high affinity agonist binding (i.e. a lower dissociation constant KH than in either the same subjects at rest or exercised controls) and also abnormal coupling to the stimulatory guanine nucleotide-binding regulatory protein (GS) of adenylate cyclase, as reflected by the inability of guanine nucleotide to convert the receptor to a low-affinity state. These findings suggest that functional alteration of the beta adrenergic receptor, in the absence of abnormal plasma catecholamine levels, might contribute to the hyperadrenergic state of MVP subjects at rest. However, desensitization of high affinity beta receptors or altered receptor-GS coupling might preserve normal adrenergic responsiveness during exercise.

Carotid baroreceptor function in dogs with chronic norepinephrine infusion

Carotid baroreceptor function, the compliance of the carotid sinus wall, and the structure of the carotid artery were examined in dogs with elevated plasma norepinephrine (2,000-4,000 pg/ml) for 28 days. The dogs with high norepinephrine were normotensive (100 +/- 4.0 versus 98 +/- 4.0 mm Hg; p greater than 0.05) with bradycardia (65 +/- 4.0 versus 87 +/- 16 beats/min; p less than 0.05) compared with normal dogs in the conscious state. However, after pentobarbital anesthesia blood pressure was significantly higher in dogs with chronic norepinephrine infusion (165 +/- 6 mm Hg) compared with normal dogs (132 +/- 6 mm Hg). To assess baroreceptor sensitivity, multiunit carotid baroreceptor activity was recorded from the right carotid sinus nerve, and the carotid sinus wall compliance (sonomicrometers) was measured during nitroglycerin and phenylephrine injections. The threshold and saturation pressures increased from 96 +/- 3.9 to 117 +/- 4.2 mm Hg and from 145 +/- 4.3 to 171 +/- 5.7 mm Hg, respectively, in the normal dogs compared with the high norepinephrine dogs. The most striking differences were the marked increases in sensitivity of carotid baroreceptors (0.47 +/- 0.05 versus 1.99 +/- 0.45 spikes.sec-1.mm Hg-1; p less than 0.01) and maximum firing frequency of the baroreceptors (24 +/- 3.1 versus 48 +/- 4.4 spikes/sec; p less than 0.01), whereas the carotid sinus wall compliance was unchanged (0.014 +/- 0.003 versus 0.012 +/- 0.002 mm/mm Hg; p greater than 0.05). Similar alterations were observed using single fiber recordings, that is, an increase in threshold and saturation pressures and slope of baroreceptor units in dogs with elevated norepinephrine. The wall thickness and area of the carotid artery were determined. Both increased significantly (0.77 +/- 0.06 versus 1.30 +/- 0.12 mm and 9.0 +/- 0.8 versus 11.9 +/- 0.9 mm2; p less than 0.05) in dogs chronically infused with norepinephrine while the dry weight-to-wet weight ratio of left carotid artery tissue also increased from 26.0 +/- 0.73% to 29.0 +/- 0.57%. These studies indicate that 1) one of the possible mechanisms responsible for bradycardia in the conscious dogs with high norepinephrine is enhanced sensitivity of carotid baroreceptors; 2) the enhanced sensitivity of carotid baroreceptors is not due to a change in compliance of the carotid sinus wall; and 3) chronic elevation of norepinephrine causes hypertrophy or hyperplasia of the wall of the common carotid artery.

Effects of aerobic exercise training on symptomatic women with mitral valve prolapse

The effects of a 12-week aerobic exercise training protocol on 32 symptomatic women with mitral valve prolapse were studied. Subjects were randomly assigned to control or exercise groups. Exercise subjects completed a 12-week (3 times per week) exercise training program based on guidelines established by the American Heart Association for phase II cardiac rehabilitation programs; control group subjects maintained normal activities. Before and after training, subjects underwent maximal multistage treadmill testing, and measurements were obtained for plasma catecholamine levels at rest and during peak exercise; they completed the State Trait Anxiety Inventory and General Well-Being Schedule. Weekly symptom frequency of chest pain, arm pain, palpitations, shortness of breath, fatigue, headache, mood swings, dizziness and syncope were monitored for the 12-week period. Data were analyzed using multivariate analysis of variance, multivariate analysis of covariance, and analysis of covariance with repeated measures. Compared with control subjects, the exercise group showed a significant (p less than 0.05) decrease in State Trait Anxiety Inventory scores, an increase in General Well-Being scores, an increase in functional capacity and a decline in the frequency of chest pain, fatigue, dizziness and mood swings. No statistically significant differences were noted in catecholamine levels at rest or during peak exercise. These findings support the use of aerobic exercise in the management of symptomatic women with mitral valve prolapse.

Major depression, panic disorder, and mitral valve prolapse in patients who complain of chest pain

PURPOSE

Patients with chest pain but without angiographic evidence of significant atherosclerotic coronary artery disease (CAD) are often found to have other medical or psychiatric disorders, including mitral valve prolapse, panic disorder (PD), and major depressive disorder (MDD). The purpose of this study was to determine the degree of comorbidity between MDD/PD and mitral valve prolapse in a group of patients with non-CAD chest pain.

PATIENTS AND METHODS

Patients referred for cardiac catheterization and coronary angiography for suspected CAD who were 70 years of age or younger and without other significant medical illnesses or cardiac complications were eligible for study. The first 100 patients who agreed to a psychiatric diagnostic interview were recruited.

RESULTS

Forty-eight of the 100 patients were found to be without significant CAD. Forty-two percent of these patients, compared to 19% of the patients with significant CAD, were found to have either MDD, PD, or both. Eighty percent of the patients without CAD who had mitral valve prolapse also had either MDD or PD (p less than 0.006).

CONCLUSIONS

The finding that mitral valve prolapse was significantly associated with MDD/PD has implications for the diagnosis and treatment of patients with non-CAD chest pain, and may explain why these patients complain of symptoms.

Role of intact cardiac nerves and reflex mechanisms in desensitization to catecholamines in conscious dogs

To study chronic catecholamine desensitization, mini-osmotic pumps were implanted subcutaneously to deliver NE, (0.5 micrograms/kg/min) or saline over 3-4 wk in dogs instrumented with left ventricular (LV) pressure gauges and arterial and left atrial pressure catheters. An acute challenge to NE (0.4 micrograms/kg/min) in intact, conscious dogs increased LV dP/dt by 1,531 +/- 208 mmHg/s before NE pumps, and by a similar amount, 1,340 +/- 166 mmHg/s, 3-4 wk after NE pumps. In contrast, an acute challenge to isoproterenol (ISO, 0.4 micrograms/kg/min) increased LV dP/dt by 5,344 +/- 532 mmHg/s before NE pumps, and significantly less (P less than 0.05; 2,425 +/- 175 mmHg/s) after NE pumps. In the presence of ganglionic and alpha 1-adrenergic blockades, NE (0.4 micrograms/kg/min) increased LV dP/dt by 3,656 +/- 468 mmHg/s before NE pumps and significantly less (P less than 0.01; 1,459 +/- 200 mmHg/s) after NE pumps. Confirming this, an acute challenge to NE (0.4 micrograms/kg/min) in dogs with arterial baroreceptor denervation increased LV dP/dt by 3,732 +/- 896 mmHg/s before NE pumps, and significantly less (P less than 0.05, 1,725 +/- 408 mmHg/s) after NE pumps. In addition, in cardiac denervated dogs, NE (0.4 micrograms/kg/min) increased LV dP/dt by 9,901 +/- 1,404 mmHg/s before NE pumps and significantly less (P less than 0.01, 2,690 +/- 306 mmHg/s) after NE pumps. Desensitization of heart rate responses to NE challenge was also more apparent in the absence of reflex mechanisms. Thus, neural reflex mechanisms play a major role in physiological expression of cardiac desensitization to catecholamines in conscious dogs.

Cardiovascular dystonia in recovered panic patients

Resting heart rate, heart rate variability and blood pressure; the heart rate and blood pressure response to standing; and the heart rate response to Valsalva's manoeuvre, have been measured in a group of 12 patients with panic disorder and a group of 12 age- and sex-matched normal subjects. The patients had undergone treatment for their panic attacks with cognitive therapy; all had responded and all had been panic-free for a minimum of 4 months (mean 7.6 months). Mood ratings (BDI, BAI and SSAI) were comparable with established norms. The patients nevertheless had a raised resting systolic blood pressure, a reduced resting heart rate and an abnormal orthostatic response.

Exercise response in young women with mitral valve prolapse

To detect for possible evidence of autonomic nervous system dysfunction, we assessed exercise response in 198 young women with echocardiographically documented MVP. The same test was used to determine whether patients with or without physical symptoms or with various auscultatory findings responded differently. Compared with 105 age- and sex-matched healthy subjects, the MVP patients showed significantly higher mean heart rate, systolic blood pressure, pulse pressure and rate-pressure (double) product, at both rest and exercise; significantly lower mean near-maximal physical working capacity (PWC170); significantly higher incidence of both arrhythmias and nonspecific ST and T wave changes; and a significantly longer mean corrected QT interval. None of these findings was associated with the presence of physical symptoms or with specific auscultatory or echocardiographic findings. These observations strongly suggest an autonomic nervous system imbalance in some young women with MVP, irrespective of whether physical symptoms are present.

Nonischemic ventricular tachycardia. Clinical course and long-term follow-up in patients without clinically overt heart disease

This report describes the clinical, laboratory, and electrophysiologic features of 52 patients with ventricular tachycardia (VT) who had no clinical evidence of heart disease. The mean age of patients was 36 years, cardiovascular collapse occurred in 18 patients (35%), and exercise-related symptoms were present in 24 of 49 patients (49%). There were 20 patients with sustained monomorphic VT, 11 with incessant VT, and 21 with nonsustained VT. Abnormalities were present in 14 of 38 patients (37%) during echocardiography and in 21 of 47 patients (45%) who underwent cardiac catheterization. During baseline evaluation while patients were not receiving antiarrhythmic drugs, ambulatory monitoring and exercise testing showed an 88% and 57% incidence, respectively, of nonsustained or sustained monomorphic VT, whereas 31 of 50 patients (62%) had inducible VT (requiring an infusion of isoproterenol in 11 patients) during programmed electrical stimulation. The clinical VT (when a 12-lead electrocardiogram was available for analysis) had a left bundle branch block (LBBB) configuration in 20 of 33 patients (61%) and a right axis deviation in 17 of 33 patients (51%). The VT occurring during exercise testing and programmed electrical stimulation had the same configuration as the clinical VT in 22 of 22 patients. Three patients have received an antitachycardia pacemaker, and one patient underwent endocardial resection. Forty-eight patients (92%) were treated medically. One patient died of cancer; the remaining 47 patients were alive at a mean follow-up of 96 months after initial symptoms and 46 months after programmed electrical stimulation. We conclude that in patients without clinical evidence of heart disease, VT may be incessant, sustained, or nonsustained and that VT originates from the right ventricular outflow tract in more than 50% of patients. Although cardiac abnormalities may be found in more than 30% of patients, the exact significance of these abnormalities is unclear because of the absence of progressive changes and the excellent prognosis of this group of patients.

Spectrum of dysautonomia in mitral valvular prolapse

PURPOSE

Symptoms suggesting altered autonomic regulation of cardiovascular function have been noted in some patients with mitral valvular prolapse (MVP) but may also occur in patients with other disorders. We evaluated cardiovascular responses to autonomic stimuli in 118 patients with symptoms of dysautonomia, 78 of whom had MVP, and 40 of whom did not, to determine if unique patterns of these responses distinguished patients in one symptomatic subgroup from another.

SUBJECTS AND METHODS

The responses of patients to standing, quantitated Valsalva maneuver, facial immersion in ice water, and administration of isoproterenol, phenylephrine, and tyramine were compared with those in 12 asymptomatic patients with MVP and 23 normal volunteers.

RESULTS

Constitutional, cardiovascular, and neuropsychiatric symptoms occurred with similar frequency in the two symptomatic patient groups. The most common pattern of abnormal responses in symptomatic patients with or without MVP was (1) an increased heart rate and elevated plasma norepinephrine levels while supine and then while standing quietly for five minutes, (2) an exaggerated increase in heart rate during phase II of Valsalva, (3) a diminished bradycardic response during phase IV of Valsalva, and (4) an exaggerated heart rate response to administration of isoproterenol. The increased heart rate during Valsalva, but not the exaggerated sensitivity to isoproterenol, was correlated with the magnitude of the chronotropic response to standing only in symptomatic patients with MVP. Exaggerated hypertensive overshoot during phase IV of Valsalva was observed in only a few symptomatic patients. No consistent pattern of these abnormalities, however, was noted in any of the patient subgroups. Hemodynamic responses to autonomic stimuli in asymptomatic MVP patients were generally indistinguishable from those observed in normal subjects.

CONCLUSION

These findings suggest that abnormal cardiovascular responses to autonomic stimuli may occur in any patient with symptoms of dysautonomia regardless of the presence or absence of MVP and that the pattern of these abnormal responses may be diverse. It is therefore important to characterize the pattern of altered autonomic regulation of cardiovascular function in each patient when considering mechanistic implications or making therapeutic decisions about these patients.

Postural exercise abnormalities in symptomatic patients with mitral valve prolapse

The hemodynamics of the supine and upright exercise response in 16 symptomatic women with mitral valve prolapse (Group I) was compared with that in 8 asymptomatic normal control women (Group II). All subjects had supine and upright echocardiography and phonocardiography at rest and none demonstrated mitral regurgitation. All participants then underwent same day graded bicycle exercise, with simultaneous radionuclide angiography in both the upright and the supine posture. Catecholamines were measured, and a variety of volumetric and hemodynamic data were obtained. Group I (patients with mitral valve prolapse) demonstrated a reduced exercise tolerance, especially during upright exercise, as measured by both total exercise duration and maximal work load achieved. Mean total catecholamine measurements were similar between the two study groups at comparable mean heart rate, mean blood pressure and mean rate-pressure (double) product. No difference was observed in the ratio of right to left ventricular stroke counts at rest or during exercise regardless of posture, suggesting that exercise-induced mitral regurgitation did not occur. A difference was noted, however, in left ventricular end-diastolic volume index. At rest, Group I patients exhibited a 42% decrease in this index when sitting upright, and this difference from supine values persisted at submaximal (300 kpm/min) and peak work loads (34 and 29% difference, respectively). This contrasted with the control subjects whose upright end-diastolic volumes at rest, at 300 kpm/min and at peak exercise were reduced 21, 10 and 3%, respectively, compared with supine values. Cardiac index measurements reflected the reduced left ventricular end-diastolic volume observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Systemic hormonal and physiological abnormalities in anxiety disorders

Among the studies of systemic hormonal and physiological abnormalities associated with anxiety disorders, the most consistent and extensive findings suggest (a) peripheral adrenergic hyperactivity (including increases in norepinephrine but not epinephrine) and functional dysregulation, (b) increased incidence of mitral valve prolapse in panic patients, and (c) normal suppressibility of the hypothalamic-pituitary-adrenal cortical endocrine system with dexamethasone in panic patients. Other less-certain findings include (a) increased circulating concentrations of plasma ACTH and/or cortisol, and prolactin, in panic patients, (b) increased platelet monoamine oxidase activity in generalized anxiety and/or panic patients, (c) decreased gonadal axis activity in some anxious individuals, (d) decreased nighttime melatonin plasma concentrations in panic patients, and (e) peripheral alpha 2 and beta-adrenoreceptor down-regulation, with normal serotonin binding parameters. These findings, taken together, provide tentative support for dysfunction in adrenergic and GABAergic central nervous system mechanisms in people with anxiety disorders. Abnormal anxiety and normal stress both show evidence of adrenergic hyperactivity; however, there appear to be differences in hormonal profiles, especially the apparent lack of increase of epinephrine during panic attacks, as well as differences in the reactivity of the system, and in the "trigger" mechanisms which determine when the response occurs.

The QT and QS2 intervals in patients with mitral leaflet prolapse

The QT interval was plotted against the R-R interval in 92 patients with mitral prolapse and 92 age- and sex-matched control subjects. Ten patients (11%) lay above the upper 95% confidence limit for the control group, and analysis of variance confirmed a small group effect (p less than 0.05). Despite this, the mean QT intervals in the two groups differed by only 7 msec and a t test showed no significant difference between the groups. The prevalence of QT prolongation was exaggerated by Bazett's rate correction formula (62%) or historical control groups published by Simonson (58%) or Ashman (70%). Simultaneous QT and QS2 intervals were measured in 67 patients with mitral prolapse. Inversion of the normal QT:QS2 relationship occurred in nine patients (13%) and was more common in the presence of severe mitral regurgitation. It was not associated with an increased prevalence of absolute QT prolongation and was therefore thought to be caused by relative shortening of the QS2 interval. In conclusion, the prevalence of QT prolongation in mitral prolapse is low (11%). The QT:QS2 ratio is unlikely to be a reliable indicator of QT prolongation in these patients.

Absence of hypertension despite chronic marked elevations in plasma norepinephrine in conscious dogs

To better define the mechanisms of blood pressure control in states of catecholamine excess, we infused norepinephrine for 28 days using subcutaneously implanted osmotic pumps in dogs previously instrumented for monitoring left ventricular dynamics and cardiac output. Plasma norepinephrine rose from 238 +/- 27 to 4346 +/- 952 pg/ml at 21 days, while epinephrine and dopamine levels did not change. Heart rate fell from 85 +/- 4 to 63 +/- 6 beats/min, while arterial pressure was unchanged from baseline. Total peripheral resistance rose 0.011 +/- 0.003 mm Hg/ml/min from a control value of 0.029 +/- 0.002 mm Hg/ml/min, and cardiac output decreased 1093 +/- 292 ml/min from a baseline level of 3575 +/- 156 ml/min. Since stroke volume did not change, the maintenance of arterial pressure is related to decreases in cardiac output secondary to bradycardia. Buffering mechanisms are responsible for maintenance of systemic arterial pressure because hexamethonium and atropine caused hypertension. Although left ventricular end-diastolic pressure, end-diastolic diameter, shortening, rate of change of pressure, velocity of myocardial shortening, cardiac work, stroke work, and the double product did not change significantly during the study, postmortem examination demonstrated biventricular hypertrophy. Thus, despite markedly elevated catecholamine levels and no elevation of systemic arterial pressure, myocardial hypertrophy developed. These studies lend support to the hypothesis that norepinephrine may be a direct myocardial tropic hormone and suggest that intense activation of reflex buffering mechanisms maintains blood pressure in the normal range during chronic catecholamine infusion.