Prolapsed mitral valve: the commonest valve disease?

Heart disease in children

Advances in the understanding of the pathophysiology, diagnosis, and medical and surgical management of neonates with cardiovascular disease has led to their improved survival rates. These improvements have resulted in an increased number of pediatric patients presenting to the primary care physician's office with underlying heart disease. Understanding the genetic, congenital, or acquired etiologies to the various pediatric heart diseases is crucial to preventing these lesions and treating these patients.

Tyrosine hydroxylase- and nitric oxide synthase-immunoreactive nerve fibers in mitral valve of young adult and aged Fischer 344 rats

Using confocal fluorescence microscopy we studied, in whole mounts of heart mitral valves of young adult and aged Fischer 344 rats, the distribution of nerves containing the catecholamine marker tyrosine hydroxylase (TH) or the synthetic enzyme marker for nitric oxide, nitric oxide synthase (NOS). TH-IR was localized in two separate nerve plexuses which do not intermingle. The 'major' plexus arose from the annulus region, traversed the basal zone of the valve, and ramified in the intermediate zone to form a dense network of fine fibers. The 'minor' plexus was restricted to the distal zone and originated from bundles that ascended the chordae tendineae to enter the valve cusp. A concentric zone located between the major and minor plexuses was devoid of TH-IR nerve fibers. Both plexuses demonstrated (i) nerves that contained numerous varicosities along the length of each fiber, (ii) many terminal axons and (iii) different shaped terminal axon endings. With age, the density of TH-IR innervation in the mitral valve was markedly reduced; and nerve fibers of the minor plexus were limited to the chordae tendinae, without extending into the valve cusp itself. NOS-IR fibers in the mitral valve formed a loose network that extended from the annulus to more than halfway down the cusp. The varicose beads of the terminal NOS-IR axons appeared to become progressively smaller and less intensely fluorescent until they disappeared at the terminal endings, which showed no specializations. No NOS-IR fibers were observed in the distal zone of the valve leaflet or in the chordae. In the aged mitral valve, the density of NOS-IR nerves was decreased, as compared with NOS-IR innervation in the young adult valve. The existence of TH and NOS as well as other signal molecule markers in heart valve nerves and the disparate patterns of their distribution and localization provide evidence supporting the theory that heart valve nerves form a complex reflexogenic control system in the mitral heart valve. In summary, two distinct neural architectures are described for TH-IR and NOS-IR valve nerves, respectively. The former are believed to be axons dedicated to sympathetic motor functions. The NOS-IR valve nerves may have sensory and/or postganglionic parasympathetic motor functions. An implication of these findings is that different, but perhaps related, valve functions may be mediated by separate, dedicated circuits.

Cause of death in an emergency department

A retrospective review was done of 601 consecutive emergency department deaths. Nontrauma causes accounted for 77% of the deaths and this group had an average age of 64 years and a male to female ratio of 1.9:1. Trauma caused 23% of the fatalities and this group had a younger average age of 29 years and a male to female ratio of 4.6:1. The most common causes of nontrauma death were sudden death of uncertain cause (34%), coronary artery disease (34%), cancer (5%), other heart disease (4%), chronic obstructive lung disease (3%), drug overdose (3%), and sudden infant death syndrome (2%). The most common causes of trauma death were motor vehicle accidents (61%) and gunshot wounds (16%). The overall autopsy rate was 40%. Death certificates were often in error.

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.

Mitral valve prolapse

Mitral valve prolapse is a common mitral valve disorder manifested clinically as a midsystolic click and/or a late systolic murmur (the click-murmur syndrome) and pathologically as billowing or prolapsing mitral leaflets (the floppy valve syndrome). Not only is it one of the two most common congenital heart diseases and the most common valve disorder diagnosed in the United States, but it is also prevalent throughout the world. Mitral valve prolapse may be associated with a variety of other conditions or diseases. Diagnosis of mitral valve prolapse should be made on clinical grounds and, if necessary, supported by echocardiography. The majority of patients with mitral valve prolapse suffer no serious sequelae. However, major complications such as disabling angina-like chest pains, progressive mitral regurgitation, infective endocarditis, thromboembolism, serious arrhythmias, and sudden death may occur. Unless these serious complications occur, most of the patients with mitral valve prolapse need no treatment other than reassurance, including those with atypical chest pain or palpitation unconfirmed by objective data. Therapy with a beta-blocker for disabling chest pain and/or arrhythmias and antiplatelet therapy for cerebral embolic events may be indicated. In occasional patients with significant mitral regurgitation surgery may be necessary.

Mitral valve prolapse with symptoms of beta-adrenergic hypersensitivity. Beta 2-adrenergic receptor supercoupling with desensitization on isoproterenol exposure

Autonomic nervous system dysfunction has recently been identified in a subset of patients with mitral valve prolapse. These autonomic nervous system abnormalities may correspond, in part, to biochemical alterations in beta-adrenergic receptors. Nine women with mitral valve prolapse and symptoms and signs of beta-adrenergic hypersensitivity and seven normal volunteer women were studied. Quiet standing (five minutes) increased both heart rate and plasma norepinephrine (p less than 0.05) in symptomatic patients with mitral valve prolapse compared with normal subjects. The dose of isoproterenol required either to increase heart rate 25 beats/minute (0.5 +/- 0.3 microgram versus 1.0 +/- 0.3 microgram) or to decrease mean arterial pressure 20 mm Hg (11.1 +/- 4.8 versus 78.2 +/- 25.2 micrograms) was significantly less in the patients with mitral valve prolapse than in the volunteers. Symptomatic patients with mitral valve prolapse were desensitized by a four-hour isoproterenol infusion, whereas sensitivity in normal control subjects did not change. In the patients with mitral valve prolapse, baseline beta-adrenergic receptor coupling was elevated compared with that in control subjects (220 +/- 7 versus 81 +/- 2; p less than 0.001). Isoproterenol infusion induced uncoupling in these patients (KL/KH = 35 +/- 3, p less than 0.05) but did not alter coupling in normal volunteers. This study demonstrates physiologic and pharmacologic beta-adrenergic hypersensitivity in vivo directly corresponding to biochemical supercoupling in a subset of patients with mitral valve prolapse.

The association of floppy mitral valve with disjunction of the mitral annulus fibrosus

Floppy mitral valve is usually attributed to connective-tissue degeneration. However, we have observed several instances in which both a floppy mitral valve and an abnormal mitral annulus fibrosus were present at autopsy. To study this association, we examined 900 hearts (after postmortem arteriography and fixation in distention) from autopsies of adults at The Johns Hopkins Hospital. Twenty-five (3 percent) of the hearts had a morphologically typical floppy mitral valve; in 23 of them (92 percent), the mitral annulus fibrosus showed disjunction--i.e., a separation between the atrial wall-mitral valve junction and the left ventricular attachment. In 42 other hearts (5 percent), which were from significantly younger patients (mean age [+/- SE], 60 +/- 2 years vs. 68 +/- 3; P less than 0.05), there was mitral annulus disjunction but no floppy mitral valve. Two hearts had a floppy mitral valve but no disjunction of the annulus; both of them had old infarcts of the papillary muscle. Our results show that floppy mitral valve is significantly associated with disjunction of the mitral annulus fibrosus (P less than 0.001). We suggest that floppy mitral valve develops from hypermobility of the valve apparatus, and that it is usually secondary to disjunction of the mitral annulus fibrosus, an anatomic variation in the morphology of the annulus.

Neurologic disorders associated with mitral valve prolapse

Mitral valve prolapse has been reported to be associated with a variety of neurologic disorders, including cerebral ischemia, transient global amnesia, migraine, autonomic dysfunction, and psychiatric disease. The evidence supporting these associations and possible pathogenetic mechanisms are discussed. Some neurologic disorders may be direct complications of mitral valve prolapse, while others may occur as part of an underlying genetic defect or common link.

Arrhythmias in patients with mitral valve prolapse. Types, evaluation, and therapy

A wide spectrum of cardiac rhythm and conduction disorders occur in patients with all types of valvular heart disease. However, certain types of valvular disease have a special predilection for arrhythmias, including atrial and ventricular tachyarrhythmias as well as bradyarrhythmias, inherent to the etiology of the condition itself. Most notable in this regard is mitral valve prolapse, in which cardiac dysrhythmia is now recognized as the complication of highest frequency. The principal purpose of this article is the delineation of the characteristics and management of rhythm disorders in the mitral valve prolapse syndrome.