Systolic ejection murmurs in the era of modern cardiology: what do we really know?

Turbulent Intensity of Blood Flow in the Healthy Aorta Increases With Dobutamine Stress and is Related to Cardiac Output

Introduction: The blood flow in the normal cardiovascular system is predominately laminar but operates close to the threshold to turbulence. Morphological distortions such as vascular and valvular stenosis can cause transition into turbulent blood flow, which in turn may cause damage to tissues in the cardiovascular system. A growing number of studies have used magnetic resonance imaging (MRI) to estimate the extent and degree of turbulent flow in different cardiovascular diseases. However, the way in which heart rate and inotropy affect turbulent flow has not been investigated. In this study we hypothesized that dobutamine stress would result in higher turbulence intensity in the healthy thoracic aorta.

Method: 4D flow MRI data were acquired in twelve healthy subjects at rest and with dobutamine, which was infused until the heart rate increased by 60% when compared to rest. A semi-automatic segmentation method was used to segment the thoracic aorta in the 4D flow MR images. Subsequently, flow velocity and several turbulent kinetic energy (TKE) parameters were calculated in the ascending aorta, aortic arch, descending aorta and whole thoracic aorta.

Results: With dobutamine infusion there was an increase in heart rate (66 ± 9 vs. 108 ± 13 bpm, p < 0.001) and stroke volume (88 ± 13 vs. 102 ± 25 ml, p < 0.01). Additionally, there was an increase in Peak Average velocity (0.7 ± 0.1 vs. 1.2 ± 0.2 m/s, p < 0.001, Peak Max velocity (1.3 ± 0.1 vs. 2.0 ± 0.2 m/s, p < 0.001), Peak Total TKE (2.9 ± 0.7 vs. 8.0 ± 2.2 mJ, p < 0.001), Peak Median TKE (36 ± 7 vs. 93 ± 24 J/m3, p = 0.002) and Peak Max TKE (176 ± 33 vs. 334 ± 69 J/m3, p < 0.001). The relation between cardiac output and Peak Total TKE in the whole thoracic aorta was very strong (R² = 0.90, p < 0.001).

Conclusion: TKE of blood flow in the healthy thoracic aorta increases with dobutamine stress and is strongly related to cardiac output. Quantification of such turbulence intensity parameters with cardiac stress may serve as a risk assessment of aortic disease development.

Standardization of Dolphin Cardiac Auscultation and Characterization of Heart Murmurs in Managed and Free-Ranging Bottlenose Dolphins (Tursiops truncatus)

Cardiac auscultation is an important, albeit underutilized tool in aquatic animal medicine due to the many challenges associated with in-water examinations. The aims of this prospective study were to (1) establish an efficient and repeatable in-water cardiac auscultation technique in bottlenose dolphins (Tursiops truncatus), (2) describe the presence and characterization of heart murmurs detected in free-ranging and managed dolphins, and (3) characterize heart murmur etiology through echocardiography in free-ranging dolphins. For technique development, 65 dolphins cared for by the Navy Marine Mammal Program (Navy) were auscultated. The techniques were then applied to two free-ranging dolphin populations during capture-release health assessments: Sarasota Bay, Florida (SB), a reference population, and Barataria Bay, LA (BB), a well-studied population of dolphins impacted by the Deepwater Horizon oil spill. Systolic heart murmurs were detected at a frequent and similar prevalence in all dolphin populations examined (Navy 92%, SB 89%, and BB 88%), and characterized as fixed or dynamic. In all three populations, sternal cranial and left cranial were the most common locations for murmur point of maximal intensity (PMI). An in-water transthoracic echocardiogram technique was refined on a subset of Navy dolphins, and full echocardiographic exams were performed on 17 SB dolphins and 29 BB dolphins, of which, 40 had murmurs. Spectral Doppler was used to measure flow velocities across the outflow tracts, and almost all dolphins with audible murmurs had peak outflow velocities ≥1.6 m/s (95%, 38/40); three dolphins also had medium mitral regurgitation which could be the source of their murmurs. The presence of audible murmurs in most of the free-ranging dolphins (88%) was attributed to high velocity blood flow as seen on echocardiography, similar to a phenomenon described in other athletic species. These innocent murmurs were generally characterized as Grade I-III systolic murmurs with PMI in the left or sternal cranial region. This study is the first to describe an efficient technique for in-water dolphin cardiac auscultation, and to present evidence that heart murmurs are common in bottlenose dolphins.

Innocent Cardiac Murmur in Puppies: Prevalence, Correlation with Hematocrit, and Auscultation Characteristics

BACKGROUND

The aims of this study were to establish the prevalence of innocent cardiac murmurs in clinically healthy puppies, to investigate a possible correlation between the presence of an innocent murmur and hematocrit, and to describe the auscultation characteristics of innocent murmurs.

HYPOTHESIS

Lower hematocrit contributes to the genesis of innocent murmurs.

ANIMALS

Five hundred and eighty-four client-owned clinically healthy puppies, between 20 and 108 days old.

METHODS

Two cross-sectional surveys with a 1-year (n = 389 pups) pilot and a half-year (n = 195 pups) principal study periods. Cardiac auscultation was performed by a single, board-certified cardiologist. Hematocrit was measured with an automatized hematology analyzer. Echocardiography was performed only on puppies with a cardiac murmur in the principal study.

RESULTS

In the pilot study, 15% of the dogs had a murmur. Innocent murmur was diagnosed in 28% of the 195 dogs in the principal study. Innocent murmurs were systolic, mostly with a musical character and with a maximal intensity of 2 of 6, and mostly with the point of maximal intensity in the left cardiac base. The hematocrit was significantly lower in the group with a murmur compared to the group without (P = .023).

CONCLUSIONS AND CLINICAL IMPORTANCE

Innocent murmur was a common finding in puppies at the age when the first veterinary controls usually take place. Physiologic anemia contributes to the genesis of innocent murmurs in puppies. Rising hematocrit in growing puppies can explain the spontaneous disappearance of innocent murmurs with aging. Hematocrit did not differentiate innocent murmurs from abnormal murmurs.

Multiphysics computational models for cardiac flow and virtual cardiography

A multiphysics simulation approach is developed for predicting cardiac flows as well as for conducting virtual echocardiography (ECHO) and phonocardiography (PC) of those flows. Intraventricular blood flow in pathological heart conditions is simulated by solving the three-dimensional incompressible Navier-Stokes equations with an immersed boundary method, and using this computational hemodynamic data, echocardiographic and phonocardiographic signals are synthesized by separate simulations that model the physics of ultrasound wave scattering and flow-induced sound, respectively. For virtual ECHO, a Doppler ultrasound image is reproduced through Lagrangian particle tracking of blood cell particles and application of sound wave scattering theory. For virtual PC, the generation and propagation of blood flow-induced sounds ('hemoacoustics') is directly simulated by a computational acoustics model. The virtual ECHO is applied to reproduce a color M-mode Doppler image for the left ventricle as well as continuous Doppler image for the outflow tract of the left ventricle, which can be verified directly against clinically acquired data. The potential of the virtual PC approach for providing new insights between disease and heart sounds is demonstrated by applying it to modeling systolic murmurs caused by hypertrophic cardiomyopathy.

Detection of innocent systolic murmurs by auscultation and their relation to hematologic and echocardiographic findings in clinically normal Whippets

OBJECTIVE

To determine murmur prevalence by auscultation of 105 apparently healthy Whippets without signs of cardiac disease, to determine the origin of these murmurs, and to evaluate the influence of sex, type of pedigree (ie, bred for showing or racing), and training on these murmurs.

DESIGN

Cross-sectional study.

ANIMALS

105 client-owned Whippets.

PROCEDURES

All dogs were auscultated by the first author and underwent a complete physical and cardiological examination, together with a hematologic assessment. Several RBC variables and echocardiographic variables were compared between dogs with or without a murmur at the level of the aortic valve.

RESULTS

44 of 105 (41.9%) dogs had no murmur. A soft systolic murmur was present with point of maximal intensity at the level of the aortic valve in 50 (47.6%) dogs, at the level of the pulmonic valve in 8 (7.6%) dogs, and at the level of the mitral valve in 3 (2.9%) dogs. No significant differences were found in heart rate, rhythm, murmur presence, point of maximal intensity, and murmur grade between males and females, between dogs with race- and show-type pedigrees, or between dogs in training and not in training. Dogs with a murmur at the level of the aortic valve had a significantly higher aortic and pulmonic blood flow velocity and cardiac output, compared with dogs without a murmur.

CONCLUSIONS AND CLINICAL RELEVANCE

Whippets have a high prevalence of soft systolic murmurs in the absence of any structural abnormalities, which fit the description of innocent murmurs. No influence of sex, pedigree type, or training was found on the occurrence of these murmurs in Whippets.

Initial clinical evaluation of cardiac systolic murmurs in the ED by noncardiologists

It is not exactly known how ED physicians perform in evaluating cardiac systolic murmurs. In 203 consecutive medical ED patients with systolic murmur, we compared the initial clinical evaluation, including auscultation, with transthoracic echocardiography. Of the 203 patients, 132 (65%) had innocent murmurs and 71 patients (35%) had valvular heart disease. Sensitivity and specificity of the initial clinical routine evaluation in diagnosing echocardiographic valvular heart disease were 82% (70%-86%) and 69% (60%-76%), respectively. Independent significant positive predictors of valvular heart disease were grade >2/6 systolic murmur (odds ratio [OR], 8.3; confidence interval [CI], 3.5-19.7, P<.001) and pathologic electrocardiogram (ECG) (OR, 8.4; CI, 3.2-22, P<.001. Patients younger than 50 years with a systolic murmur graded < or =2/6 had innocent murmurs in 98%. The initial clinical evaluation, including auscultation, by experienced ED physicians in internal medicine distinguishes well between innocent murmurs and valvular heart disease in medical patients with cardiac systolic murmurs.

Ventricular septal defect and multiple aneurysms

A 41-year-old man with a small perimembranous ventricular septal defect (VSD) developed aneurysms and aortic elongation, tortuosity and dissecting aneurysm. The asymptomatic VSD, without pulmonary circulatory disturbance, was considered hemodynamically benign and too small to warrant surgical closure. However, prolonged strenuous sporting activities could have potentiated premature development of aortic sclerosis and the unusual vascular lesions secondary to the VSD, and an injury may have precipitated mural dissection in the vulnerable aortic wall. Clinicopathological analysis of the unusual complications associated with the VSD suggests that closure of the defect at an early age should be considered to possibly obviate premature degenerative, valvular and vascular changes in adulthood and also secondary endocardial infection.

Bedside cardiac examination: constancy in a sea of change

The general trend in the recent literature has been to highlight the difficulties and shortcomings of the physical examination and to attribute these difficulties to deficiencies in training rather than to intrinsic weaknesses in auscultation itself. The call is for better training. Given the advice of the authors mentioned above, individual training may be warranted at the postgraduate level and in the large community of practicing internists and cardiologists. Although not proven, it is likely that individual training with computer technology, audiotape instruction, or simulator technology such as described in the following paragraphs would be effective at improving bedside clinical diagnosis and cost-effective patient care in the postgraduate, continuing medical education setting. The advances in auscultation during the last few years have been more incremental than fundamental. There is ongoing research into the mechanism of production of S3 and S4, and mathematical modeling techniques have recently been used with some success in evaluating the vibrations of S3 and S4 as forced, damped oscillations of a viscoelastic system. Analysis of sound energy with the technique of spectral waveform analysis, which investigates the frequency content of sound signals, has been used for many years in the study of cardiovascular sound. By the use of various methods of mathematical analysis, investigators have found potentially useful information in spectral sound patterns of prosthetic valves, murmur characteristics, and even potentially hemodynamic information from heart sounds. Despite the mathematical advances, there are still disturbing drawbacks to some of the analytic techniques, such as the production of mathematical terms containing "negative energy." Although the potential of obtaining significant clinical information from spectral analysis of heart sound recordings is attractive, the clinical usefulness of such techniques remains virtually nonexistent. Similar to the recent advances in auscultation, the technical advances in the design of the stethoscope have also been more incremental than fundamental. There are at least 3 recently introduced electronic stethoscopes that have the capability of amplification and filtration and that claim noise reduction. Because their introduction is recent, no information is available in the peer-review literature regarding their clinical performance; therefore their place in the clinical arena remains to be elucidated--perhaps a boon for patient care providers with specific hearing defects and perhaps useful in noisy clinical environments. Peer-review literature has not shown clear superiority of one type of acoustic stethoscope over another. The teaching of auscultation has been an area of recognized importance in patient care since the inception of auscultation as a medical art. Attempts to facilitate practitioner learning in the performance and interpretation of auscultation have advanced through the decades limited only by the technical infrastructure of the day. The availability of recorded heart sounds and murmurs appeared shortly after the availability of recording and playback devices, with first vinyl and later tape recordings. In 1974, technology was employed to create a virtual patient named "Harvey," an engineered cardiology patient simulator that reproduces many of the physical findings of the cardiology examination. Later, with the advent of commercially available CD-ROM devices, newer, better-integrated teaching devices have been developed, some of them outstanding in their clarity and quality. Despite the obvious value of such instructional aids that are best used in the individual setting, there is evidence that the classroom is still of significant value in teaching auscultation. However, nowhere else in the practice of medicine is a mentor approach more valuable than in learning auscultation. (ABSTRACT TRUNCATED)

Echocardiography in the evaluation of systolic murmurs of unknown cause

PURPOSE

Systolic murmurs are common, and it is important to know whether physical examination can reliably determine their cause. Therefore, we prospectively assessed the diagnostic accuracy of a cardiac examination in patients without previous echocardiography who were referred for evaluation of a systolic murmur.

SUBJECTS AND METHODS

In 100 consecutive adults (mean [+/- SD] age of 58 +/- 22 years) who were referred for a systolic murmur of unknown cause, the diagnostic accuracy of the cardiac examination by cardiologists (without provision of clinical history, electrocardiogram, or chest radiograph) was compared with the results of echocardiography.

RESULTS

The echocardiographic findings included a normal examination (functional murmur) in 21 patients, aortic stenosis in 29 patients, mitral regurgitation in 30 patients, left or right intraventricular pressure gradient in 11 patients, mitral valve prolapse in 11 patients, ventricular septal defect in 4 patients, hypertrophic obstructive cardiomyopathy in 3 patients, and associated aortic regurgitation in 28 patients. In 28 (35%) of the 79 patients with organic heart disease, more than one abnormality was found; combined aortic and mitral valve disease was the most frequent combination (n = 22). The sensitivity of the cardiac examination was acceptable for detecting ventricular septal defect (100% [4 of 4]), isolated mitral regurgitation (88% [26 of 36]), aortic stenosis (71% [21 of 29]), and a functional murmur (67% [14 of 21]), but not for intraventricular pressure gradients (18% [2 of 11]), aortic regurgitation (21% [6 of 28]), combined aortic and mitral valve disease (55% [6 of 11]), and mitral valve prolapse (55% [12 of 22]). In 6 patients, the degree of aortic stenosis was misjudged on the clinical examination, mainly because of a severely diminished left ventricular ejection fraction. Significant heart disease was missed completely in only 2 patients.

CONCLUSION

In adults with a systolic murmur of unknown cause, a functional murmur can usually be distinguished from an organic murmur. However, the ability of the cardiac examination to assess the exact cause of the murmur is limited, especially if more than one lesion is present. Thus, echocardiography should be performed in patients with systolic murmurs of unknown cause who are suspected of having significant heart disease.