GENESIS AND TYPES OF HEART MURMURS

TOP ABSTRACT GENESIS AND TYPES OF... DETECTION OF A HEART... GENERAL MEDICAL TREATMENT OF... DENTAL TREATMENT CONSIDERATIONS CONCLUSION REFERENCES

 
Murmurs are defined as sounds heard in addition to the sequence of two to three heart sounds during each heartbeat.¹ The two normal heart sounds–the first heart sound (S₁) and the second heart sound (S₂)—are produced mainly by the closure of the atrioventricular (tricuspid and mitral) and semilunar (aortic and pulmonary) valves, respectively. Occasionally, an additional heart sound associated with the ventricles filling up with blood may be heard. It is referred to as S₃ when it occurs in early diastole and S₄ when heard in late diastole after the atrial contraction.

Heart murmurs can be systolic, diastolic or continuous (Box 1), and they can be reported with accompanying intensity grades (Box 2). When clinically insignificant, murmurs are referred to as being "innocent"; they are caused by increased flow or turbulence across anatomically normal valves. Some systolic murmurs may be clinically innocent, while all diastolic and continuous murmurs are abnormal.²

In cyanotic lesions, a portion of nonoxygenated blood never reaches the lungs; instead, it is shunted to the systemic circulation. Examples include transposition of great arteries, tetralogy of Fallot and single ventricle. Certain people with congenital heart disease have a characteristic body habitus, such as patients with trisomy 21 (Down syndrome). They have an increased prevalence of atrial or ventricular septal defects and tetralogy of Fallot.³

Furthermore, congenital heart disease is associated with heritable connective tissue disorders such as osteogenesis imperfecta,⁴ Ehlers-Danlos syndrome, Marfan syndrome⁵ and Stickler’s syndrome.⁶

Because patients with congenital lesions often are at a high risk of developing IE, dentists should familiarize themselves with such conditions and make sure that affected patients are given appropriate antibiotic prophylaxis before undergoing dental procedures.⁷

As shown in Box 3, some noncyanotic lesions confer a moderate risk of developing IE after dental procedures (for example, primum atrial septal defect [ASD], ventricular septal defect and patent ductus arteriosus), while others confer a low risk (for example, secundum ASD).⁸

Acquired lesions. Worldwide, the most common cause of clinically significant heart murmurs is rheumatic heart disease (RHD). In the United States and Canada, however, RHD is an uncommon finding except among recent immigrants. The most common causes of clinically significant murmurs in this country are degenerative valvular disorders such as senile calcific aortic stenosis (AS) and mitral valve prolapse (MVP).^9,10 Less common causes of acquired valvular disease are systemic lupus erythematosus (SLE)¹¹ and certain medications used in weight loss programs.¹²

Rheumatic heart disease. RHD is triggered by group A streptococcal pharyngitis. The microorganism induces an autoimmune reaction that may lead to valvular scarring and calcifications, especially involving the mitral valve. The most common forms of RHD are mitral stenosis and aortic insufficiency, both of which produce diastolic murmurs.

Aortic stenosis. Owing to aging, an initially normal trileaflet aortic valve may undergo calcific degeneration. Subsequent narrowing of the aortic valve orifice results in the clinical manifestations of AS in the elderly.¹³ When calcific aortic stenosis is encountered in middle-aged people, the clinician should suspect a diagnosis of congenitally bicuspid aortic valve (BAV). BAV is the most common form of congenital heart disease, occurring in 1 to 2 percent of all live births.⁸

Mitral valve prolapse. Myxomatous degeneration of valve leaflets, typically those of the mitral valve, results in leaflet redundancy and systolic billowing of one or both leaflets into the left atrium (compare the appearance of a normal mitral valve in Figure 1 [page 351] with that of a valve affected by myxomatous degeneration leading to mitral valve prolapse in Figure 2 [page 351]). Sometimes, this is accompanied by regurgitation. Although the prognosis for MVP is good in general, it is the valvular disease that necessitates the most valve surgery in the United States. In cases in which MVP is associated with regurgitation, a murmur often will be heard preceded by a systolic click.^14,15 Antibiotic prophylaxis is warranted for patients with MVP only when mitral regurgitation is present (Box 3).

View larger version (71K): [in this window] [in a new window]   Figure 1. Mitral valve leaflets (arrow) are seen as a thin undulating membrane separating the left atrium (LA) from the left ventricle (LV) during systole.

View larger version (54K): [in this window] [in a new window]   Figure 2. Mitral valve prolapse is characterized by excessive billowing of one or more segments of a mitral leaflet (arrows) into the left atrium (LA) and away from the left ventricle (LV) during systole.

The prevalence of heart murmurs associated with SLE ranges from 18 to 50 percent.¹⁸ However, the exact risk of contracting IE among patients with SLE is unknown.¹¹

Diet medications. Dexfenfluramine and fenfluramine-phentermine used for weight reduction have been implicated in the development of valvulopathy and valvular regurgitation.¹⁹ According to the U.S. Food and Drug Administration criteria, valvulopathy may be considered to be due to diet medication if the patient develops at least mild aortic regurgitation, moderate mitral regurgitation or both after initiating the diet drug therapeutic regimen.²⁰

In the largest study to date, mild or greater aortic regurgitation was present in 8.8 percent of treated patients and in 3.6 percent of control patients. Moderate or greater mitral regurgitation was present in 2.6 percent of treated patients and in 1.5 percent of control patients. The authors of that study concluded that valvulopathy developed primarily in patients who had taken fenfluramine-phentermine for more than six months, and it resulted predominantly in mild aortic regurgitation.²¹ Valvular regurgitation did not progress in the three to five months after discontinuation of dexfenfluramine therapy, at least not in patients who had been treated with the drug for less than three months.²²

Radiation therapy. Clinicians may treat patients with heart defects that have been acquired as a result of undergoing radiation therapy to the mediastinal region for Hodgkin’s and non-Hodgkin’s lymphomas or cancers of the breast, lung and esophagus.

Radiation injury leads to fibrotic changes with or without calcifications of the heart valves. The pathophysiology of these changes is not well-understood. However, it is known that radiation may induce valvular regurgitation, stenosis or both, which may be progressive in nature. The prevalence of valvular fibrosis is 70 to 80 percent in patients who have received cumulative radiation doses of more than 35 gray.²³

A recent study of asymptomatic patients who had undergone mediastinal irradiation attempted to estimate the clinical significance of valvular pathology.²⁴ For patients who received radiation treatment within the 10 years preceding the study, 13 patients needed to be screened to detect one candidate with valvular lesions severe enough to require endocarditis prophylaxis. Among those who were treated at least 20 years before the study (when radiation dosages were much larger than those used currently), only 1.6 patients needed to be screened to detect one candidate with significant valvular disease. Echocardiography, therefore, is strongly recommended for patients with a history of mediastinal irradiation to screen for potential valvular heart disease.

In addition to developing valvular defects, these patients may develop pericardial effusion and thickening, and they are at an increased risk of developing premature coronary artery disease.

Endocrine conditions. Patients with active or treated acromegaly have a high prevalence of mitral and aortic valve abnormalities characterized by fibrosis and/or calcifications of valve annulus and leaflets, which may lead to valvular regurgitation or stenosis.²⁵

All of the above-mentioned forms of acquired valvular disease confer a moderate risk of developing IE after dental procedures. Some forms of acquired valvular disease, however, carry a much higher risk. These include a history of IE and valve surgery (Box 3).

	DETECTION OF A HEART MURMUR

TOP ABSTRACT GENESIS AND TYPES OF... DETECTION OF A HEART... GENERAL MEDICAL TREATMENT OF... DENTAL TREATMENT CONSIDERATIONS CONCLUSION REFERENCES

 
Using a stethoscope, clinicians first detect murmurs via auscultation, and they often characterize them further through ultrasound imaging of the heart (that is, echocardiography).

Auscultation. The most common abnormal auscultatory finding on cardiac examination is a systolic murmur, which occurs in 80 to 96 percent of children and in 15 to 44 percent of adults.²⁶ These murmurs can be functional (innocent) or pathological.

Attenhofer Jost and colleagues²⁶ suggested that all patients who have a systolic murmur associated with dyspnea, chest pain or lower-extremity edema should be suspected of having a pathological murmur. These cardiac signs and symptoms can be determined easily when the oral health care provider reviews systems with the patient. Dentists should refer patients with symptomatic murmurs to a cardiologist for further evaluation.

The most common abnormal auscultatory finding on cardiac examination is a systolic murmur.

In one study, Roldan and colleagues²⁷ reported that auscultation had a sensitivity of 70 percent and a specificity of 98 percent for detecting valvular heart disease in subjects without symptoms, in comparison with echocardiography. A well-trained and experienced cardiologist can differentiate a functional (innocent) murmur from a pathological one in almost all cases.²⁸ However, according to a study by Gaskin and colleagues,²⁹ auscultation skills are suboptimal among modern medical trainees, who were able to correctly diagnose a murmur in only 33 percent of cases.

The current American College of Cardiologists/American Heart Association guidelines for the treatment of patients with valvular heart disease state that cardiac auscultation remains the most widely used technique of screening for heart disease, and that a careful observer will be able to deduce the correct origin and significance of a heart murmur.⁹ The physician should use echocardiography to confirm an impression or diagnosis of structural heart disease.

Echocardiography. Echocardiography is a diagnostic test that uses ultrasound waves to make images of the heart chambers, valves and surrounding structures. The purpose of echocardiography with regard to heart murmurs is to evaluate the primary lesion in terms of cause and severity, define the lesion’s hemodynamic significance, detect coexisting abnormalities, evaluate the size and function of cardiac chambers and establish a reference point for future comparisons.

The standard echocardiography is called transthoracic echocardiography (TTE). In this procedure, the clinician performs cardiac imaging after placing an ultrasound probe on various points on the external chest and abdominal walls.

During transesophageal echocardiography (TEE), the heart and large vessels are imaged after a small ultrasound probe is introduced into the esophagus and stomach (Figure 1). It is considered an invasive procedure and should be used only when information beyond that obtained from conventional TTE is needed.

Overall, TTE has a lower sensitivity (60 to 70 percent) than does TEE (75 to 95 percent) in detecting infective endocarditis, particularly that of left-sided (mitral and aortic) valves.³⁰ However, for the detection of infective endocarditis of the tricuspid valve, TTE often is as sensitive as TEE.³¹

Both TTE and TEE are capable of M-mode, two-dimensional and Doppler imaging (Figure 3). Once echocardiographic images are acquired and stored on a videotape or computer disk, the cardiologist analyzes the examination findings and writes a report. The major components of this report are discussed below.

View larger version (69K): [in this window] [in a new window]   Figure 3. During transesophageal echocardiography, color Doppler imaging is used to visualize a highly mosaic jet of mitral regurgitation (arrow), which begins in the left ventricle (LV) and empties into the left atrium (LA) during systole.

View larger version (64K): [in this window] [in a new window]   Figure 4. A large Staphylococcus aureus vegetation (arrows) is seen on the left atrial (LA) side of the mitral valve. LV: Left ventricle.

The information regarding chamber sizes and wall thickness often is obtained via M-mode echocardiography. A descriptive section of the report follows the numeric data in which specific cardiac pathology (if present) is mentioned, and its hemodynamic significance is discussed based on the data from all echocardiographic imaging modalities.

One of the most important parameters of cardiac function is the left ventricular ejection function. An ejection fraction below 50 percent suggests left ventricular systolic dysfunction (that is, decreased left ventricular contractility).

As for valvular function, it is important for dentists to note that a mild degree of mitral, tricuspid and pulmonic regurgitation is present in a significant percentage of healthy patients.³⁴ This finding is considered to be physiologic, is not associated with audible murmurs and, in principle, does not require any specific medical intervention.

	GENERAL MEDICAL TREATMENT OF PATIENTS WITH MURMURS

TOP ABSTRACT GENESIS AND TYPES OF... DETECTION OF A HEART... GENERAL MEDICAL TREATMENT OF... DENTAL TREATMENT CONSIDERATIONS CONCLUSION REFERENCES

 
The clinician’s approach to treating patients with heart murmurs depends on many variables, including the characteristics of the murmur itself (such as the intensity and type of murmur) and the presence or absence of cardiac symptoms.

For example, an extensive work-up is not necessary for patients with grade 1 and 2 midsystolic murmurs if they are children or young adults in whom the cardiac examination results are normal, and who do not have other signs and symptoms associated with cardiac disease.⁹

However, if patients have signs and symptoms indicating the presence of IE, thromboembolism, congestive heart failure, myocardial infarction or syncope, echocardiography is indicated.

The classic symptoms of cardiac disease include chest pain or chest discomfort, dyspnea, palpitations and syncope.^9,26 In the review of systems, clinicians must ask these key questions, the answers to which will give them clues regarding whether the murmur is innocent or clinically significant.

As noted above, mild regurgitation of the mitral, tricuspid or pulmonic valves frequently is detected in asymptomatic patients, often in the absence of an audible murmur on auscultation. In principle, such patients do not require routine antibiotic prophylaxis before dental and other bacteremia-inducing medical procedures.³⁴

In the work-up of a patient with a pathological heart murmur, echocardiography is mandatory to confirm the diagnosis, establish the severity of the lesion and assess ventricular function and size.

All health professionals, including dental professionals, should educate their patients who have clinically significant heart murmurs about antibiotic prophylaxis, while cardiologists and other physicians should counsel patients about functional limitation, exercise and work restrictions, and pregnancy issues.

The classic symptoms of cardiac disease include chest pain or chest discomfort, dyspnea, palpitations and syncope.

	DENTAL TREATMENT CONSIDERATIONS

TOP ABSTRACT GENESIS AND TYPES OF... DETECTION OF A HEART... GENERAL MEDICAL TREATMENT OF... DENTAL TREATMENT CONSIDERATIONS CONCLUSION REFERENCES

 
When treating patients with murmurs, dental professionals should take into account the fact that many patients (particularly the elderly) are unaware of their murmurs or are unwilling to report them.³⁵ This is a growing concern because older patients, particularly men, have an increased prevalence of valvular heart disease.³⁶

A consultation with the patient’s cardiologist or primary care physician should include inquiries about the type of murmur, its cause and plans for medical treatment. If echocardiography has been performed, the patient’s dentist should request a copy of the report. Details regarding valvular pathology, its hemodynamic significance and the presence or absence of any associated cardiac disease usually are stated in the report’s conclusions. Although the dentist is not expected to establish a cardiology diagnosis or provide medical recommendations, the information in the report broadens his or her understanding of a patient with a heart murmur.

It is beyond the scope of this article to discuss each and every condition associated with a heart murmur, and we address only the most common ones below. Readers are advised to seek additional information when treating patients with heart conditions that are not addressed in this article.³⁷

When treating all patients with medically complex conditions, dental professionals need to address the following four concerns:

– hemostasis;

– the patient’s susceptibility to developing IE;

– drug actions and interactions;

– the patient’s ability to tolerate the stress and trauma associated with dental procedures.³⁸

Hemostasis. Worldwide, probably the most common cause of atrial fibrillation (AF) is rheumatic mitral valve disease. In the industrialized world, however, nonvalvular causes such as age, hypertension, diabetes mellitus and congestive heart failure are much more common. AF may be associated with both systolic and diastolic murmurs (Table). Because the condition puts the patient at risk of developing thromboembolic events, anticoagulation with warfarin (rather than antiplatelet therapy with aspirin) is the preferred form of treatment.³⁹ An international normalized ratio (INR) of less than 3.5 or a prothrombin time (PT) of less than 20 seconds is recommended for routine dental care.⁴⁰

The anticoagulation effect of warfarin can be increased with numerous medications used in dentistry. Although the risk of bleeding may increase after drug interactions, this might not be reflected by the INR or PT. These interactions are complex and may vary depending on the dosage, duration, intermittent versus long-term use and other factors.

Medications of concern include long-term use of acetaminophen; antibiotics such as metronidazole, erythromycin, cephalosporins, tetracycline and penicillin; and antifungal agents such as fluconazole and ketoconazole. An additive anticoagulant effect also is seen when aspirin-containing medications or nonsteroidal anti-inflammatory drugs are used simultaneously with warfarin.

Patient’s susceptibility to IE. The American Heart Association has put forth recommendations regarding antibiotic prophylaxis for patients with specific heart conditions.⁷ The most common valvular conditions in a dental patient are aortic stenosis and mitral valve prolapse. Box 3 lists the specifics of antibiotic prophylaxis.

Drug actions and interactions. Apart from anticoagulation medications, digitalis glycosides (which may be used to treat patients with AF and congestive heart failure) are of particular concern because they have a narrow therapeutic range and exhibit numerous drug interactions. Antimicrobial agents used in dentistry, such as tetracycline, clarithromycin, erythromycin and ketoconazole, have been associated with increasing serum digoxin concentrations.

Tolerance to stress of dental procedure. Patients with heart murmurs may have accompanying symptoms of dyspnea, fatigue, orthopnea (labored breathing that occurs when lying supine and is relieved by sitting up), paroxysmal nocturnal dyspnea, palpitations and chest pains. Patients complaining of orthopnea need to be placed in a more upright position during dental treatment. The use of a rubber dam may be contraindicated in such patients, because it may restrict their ability to obtain an adequate volume of air. Appointments should be short and preferably in the late morning or early afternoon.

Anxiety can precipitate cardiac complications. The administration of nitrous oxide with adequate oxygen is safe and recommended for severely apprehensive patients.⁴¹ Adequate pain control also is important because endogenous catecholamine release increases with pain. The use of local anesthetic with epinephrine is not contraindicated in patients with AF. Although clinicians should evaluate each case separately, an evidence-based review of epinephrine did not indicate any contraindications for its use in patients with hypertension.⁴²

Beyond the provision of oral care, dental professionals are able to monitor certain cardiovascular conditions such as hypertension and, in collaboration with cardiologists and other medical professionals, screen for possible changes in the cardiac status of patients with heart murmurs.⁴³

	CONCLUSION

TOP ABSTRACT GENESIS AND TYPES OF... DETECTION OF A HEART... GENERAL MEDICAL TREATMENT OF... DENTAL TREATMENT CONSIDERATIONS CONCLUSION REFERENCES

 
Treating dental patients with heart murmurs can be challenging. Such patients may have multiple health problems that need to be addressed for dental professionals to provide safe and appropriate dental care. Dental clinicians should pay special attention to the patient’s medical history and review of systems.

Dental clinicians are not expected to establish a cardiology diagnosis or provide medical recommendations to patients. Such decisions should be left to a cardiologist or another physician. We have provided in-depth background information to broaden clinicians’ understanding of heart murmurs in their patients. By delivering dental care to this patient population, oral health care providers become part of their patients’ overall health care team.