View source for WBR0427

 {{WBRQuestion
|QuestionAuthor= {{YD}} (Reviewed by  {{YD}} and  {{AJL}})
|ExamType=USMLE Step 1
|MainCategory=Physiology
|SubCategory=Cardiology
|MainCategory=Physiology
|SubCategory=Cardiology
|MainCategory=Physiology
|SubCategory=Cardiology
|MainCategory=Physiology
|MainCategory=Physiology
|MainCategory=Physiology
|SubCategory=Cardiology
|MainCategory=Physiology
|SubCategory=Cardiology
|MainCategory=Physiology
|SubCategory=Cardiology
|MainCategory=Physiology
|SubCategory=Cardiology
|MainCategory=Physiology
|MainCategory=Physiology
|SubCategory=Cardiology
|Prompt=A 25-year-old man with a history of hypertrophic cardiomyopathy (HCM) presents to the cardiologist’s office for an annual-check up. The patient has no complaints. He receives daily verapamil for his HCM and does not report any drug-related adverse effects. Physical examination is remarkable for a murmur on cardiac auscultation. Which of the following bedside maneuvers will most likely increase the intensity of this patient’s murmur?
|Explanation=Hypertrophic cardiomyopathy (HCM) is an autosomal dominant genetic disorder characterized by obstruction of the dynamic left ventricular outflow tract that results from an asymmetric myocardial hypertrophy. It is caused by a mutation in the gene that encodes cardiac sarcomeres. Cardiac auscultation of patients with HCM is classically remarkable for a high-pitched crescendo-decrescendo mid-systolic murmur similar to that of aortic stenosis. Unlike the murmur of aortic stenosis, the cardiac murmur in HCM does not typically radiate to the carotids. Optimally, a "dynamic" cardiac auscultation for patients who are suspected to have HCM should be conducted. A [[Valsalva maneuver]] is done when a patient stands from a seated position. Valsalva maneuver decreases venous return and preload. While the majority of heart [[murmurs]] decrease in intensity upon [[Valsalva maneuver]], the intensity of murmurs caused by [[mitral valve prolapse]] (MVP) and [[HCM]] increases. During Valsalva maneuver (standing), preload decreases, which results in a reduction in the left ventricular filling. Consequently, the size of the mitral outlet is reduced, and the dynamic gradient and murmur intensity are increased. While Valsalva maneuver may not always be associated with an audible increase in murmur intensity, the stand-squat-stand maneuver may be used to further accentuate the murmur intensity. Squatting reduces both after and preload, and the murmur intensity is thus markedly decreased. Patients then stand, and the murmur intensity progressively increases. The accentuated difference in intensity between cardiac murmurs during squatting and standing allows physicians to appreciate the cardiac murmur more readily. 
|AnswerA=Standing from a seated position
|AnswerAExp=Standing from a seated position (Valsalva maneuver) increases the intensity of murmur caused by HCM.
|AnswerB=Clenching fists forcefully
|AnswerBExp=Clenching fists forcefully (hand grip) increases systemic vascular resistance and afterload.  Mitral regurgitation (MR) and ventricular septal defect (VSD) murmur intensities increase with hand grip.
|AnswerC=Lying in supine position and raising legs upwards
|AnswerCExp=Lying in supine position and raising legs upwards is the opposite of a [[Valsalva maneuver]]. It will increase preload and decrease the intensity of the HCM murmur.
|AnswerD=Rapid squatting
|AnswerDExp=Rapid squatting increases both preload and afterload, which markedly decreases the intensity of the HCM murmur.
|AnswerE=Lying in the left lateral decubitus position
|AnswerEExp=Lying in the left lateral decubitus position may help in the auscultation of murmurs caused by mitral stenosis (MS), commonly a complication of rheumatic heart disease. Auscultation using the bell of the stethoscope while patients are in a left lateral decubitus position may also identify S3 sounds, which are late diastolic, low-frequency sounds.
|EducationalObjectives=The majority of heart [[murmurs]] decrease in intensity upon [[Valsalva maneuver]] with the exception of murmurs caused by [[mitral valve prolapse]] (MVP) and [[HCM]].
|References=Ommen SR, Nishimura RA. Hypertrophic cardiomyopathy. Curr Prob Cardiol. 2004;29(5):239-91.<br>
First Aid 2014 page 272
|RightAnswer=A
|WBRKeyword=Valsalva maneuver, Murmur, Hypertrophic cardiomyopathy, HCM, Preload
|Approved=Yes
}}