Saturday, 6 December 2014

Myocardial bridge

A myocardial bridge occurs when one of the coronary arteries tunnels through the myocardium rather than resting on top of it. This is generally confined when myocardial tissue covers part of the mid left anterior descending artery (LAD), resulting in a tunneled arterial segment, which can be regarded as a congenital variant. It usually has a benign prognosis, but in some cases myocardial ischemia, infarction and sudden cardiac death have been reported. Typically, the arteries rest on top of the heart muscle and feed blood down into smaller vessels that populate throughout the myocardium. But if the muscle grows around one of the larger arteries, then a myocardial bridge is formed.

Myocardial bridging is most commonly observed of the LAD (figure).
The depth of the vessel under the myocardium is more important that the length of the myocardial bridging. There is debate, whether some of these myocardial bridges are hemodynamically significant. image from: http://rad.desk.nl/en/p48275120e2ed5

As the heart squeezes to pump blood, the muscle exerts pressure across the bridge and constricts the artery. This defect is present from birth. It can lead to uncomfortable, powerful heartbeats and angina. The incidence of the condition in the general population is estimated at 5% based on autopsy findings, but significance when found in association with other cardiac conditions is unknown. Myocardial bridging occurs frequently in patients with hypertrophic cardiomyopathy, with a prevalence as high as 30%.

The condition is diagnosed on a scaled based on what percentage of obstruction occurs. If there is less than 50% blockage, then the condition is probably benign. A result of at least 70% usually causes some pain. Small amounts of myocardial bridging often are undetectable, as the blood usually flows through the coronary while the heart is relaxing in diastole. The degree of coronary obstruction by the myocardial bridge depends on such factors as location superficial' or ‘deep', thickness, length of the muscle bridge, and degree of cardiac contractility.

Clinical significance

Because myocardial bridging is a common finding at autopsy of normal subjects, it had been thought to be a benign anatomic variation. Although this malformation is present at birth, symptoms usually do not develop before the third decade; the reason for this is not clear. Bridging of the coronary arteries was observed after administration of drugs, such as nitroglycerin or a b-agonist, in up to 40% of patients with angina pectoris and normal coronary arteries. The diagnosis of clinically important myocardial bridging should be considered in patients who have angina and do not have the traditional risk factors and the evidence of ischemia. However, objective signs of ischemia cannot always be demonstrated in patients with myocardial bridging, most likely because of a large variability.

Complications

This condition can cause complications such as vasospasm, angina pectoris, arrhythmia, Ventricular tachycardia. Additionally many patients express discomfort in specific positions, (i.e. lying on the left side for a prolonged period of time).

Infarction Due to Myocardial Bridging

Karam Souibri, M.D., and Gilles Grollier, M.D.
N Engl J Med 2005; 353:1147September 15, 2005DOI: 10.1056/NEJMicm1050647
A 45-year-old man with dyslipidemia had a sudden onset of retrosternal chest pain and presented to the emergency department. Findings on the physical examination were unremarkable. His electrocardiogram showed ST-segment elevation in the anterior leads (Panel A). Coronary angiography was immediately performed. The left anterior descending (LAD) coronary artery and two large diagonal branches appeared to be normal during diastole (Panel B) but were severely compressed during systole (Panel C), suggesting compression by myocardial bridging. A rate of flow classified as grade 2 (according to the criteria of the Thrombolysis in Myocardial Infarction [TIMI] trial) was observed in these three arteries. The other coronary arteries were normal. Direct stenting of the intramyocardial segment of the LAD artery and the second large diagonal branch restored TIMI grade 3 flow and relieved the chest pain, with normalization of the electrocardiogram. The creatine kinase and troponin levels were elevated.

Treatment

Therapeutic approaches that have been attempted for myocardial bridging include b-blockers, calcium channel blockers, stents, minimally invasive coronary artery bypass grafting (CABG), and surgical myotomy. Nitrates generally should be avoided because they increase the angiographic degree of systolic narrowing and can lead to worsening of the symptoms. B-blockers decrease the tachycardia and increase diastolic time, with a decrease in contractility and compression of the coronary arteries. Thus, these agents should be beneficial, although they have not been studied in randomized controlled trials.

REFERENCES:
http://en.wikipedia.org/wiki/Myocardial_bridge
http://eurheartj.oxfordjournals.org/content/ehj/26/12/1159.full.pdf

Wednesday, 10 September 2014

Dr. Ken Grauer - ECG Video-3 (Blog #97) - A Patient with SVT and marked ST Depression (September 9, 2014)

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     This is the 3rd installment of my ECG Video Blog. This 11-minute video features a case of a patient with SVT (SupraVentricular Tachycardia) with chest pain and marked ST depression on his 12-lead ECGPlease give me Feedback on how you like these ECG Video-Blogs!
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NOTE: There are advantages to using a video format format. These include:
  • Ability to illustrate concepts not done full justice by the written word.
  • Greater dispersion of my content through Google & YouTube. This material is free for anyone to use.
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LINK to my ECG Video-Blogs and other ECG Resources (including Power Point Shows of my video blogs):
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The patient is a previously healthy 60-year old man who presented with palpitations and new-onset chest pain. He was on no meds — and had no prior history of heart disease. BP = 70 systolic at the time the 12-lead ECG in Figure-1 was obtained.
  • What is the rhythm in Figure-1?
  • Why so much ST segment depression?
  • What are your diagnostic considerations?
  • What would you do?

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GT– http://youtu.be/5E3_MKuvr9c on YouTube to view this ECG Video (11 minutes).


Sunday, 31 August 2014

Dr. Ken Grauer - ECG Video-2 (Blog #96) - ECG Diagnosis of BBB (August 31, 2014)



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     This is the 2nd installment of my ECG Video Blog. This 17-minute video reviews how to make the ECG diagnosis of BBB (Bundle Branch Block) in 5 seconds or less. Please Give Me Feedback (ekgpress@mac.com) as to whether you like this new Video format.
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NOTE: There are advantages to using a video format format. These include:
  • Ability to illustrate concepts not done full justice by the written word.
  • Greater dispersion of my content through Google & YouTube. This material is free for anyone to use.
-----------------------------------------
LINK to my ECG Video-Blogs and other ECG Resources (including Power Point Shows of my video blogs):
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ECG Diagnosis of the bundle branch blocks can be simplified — and readily accomplished with accuracy in seconds. This is because: i) There are only 3 "answers" ( = typical LBBB; typical RBBB; or neither = IVCD); and ii) You only need to look at 3 leads to diagnose the type of BBB ( = leads I, V1, V6— as shown in the Figure below.

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GTO – https://www.youtube.com/watch?v=WQHzbZXcU4Y on YouTube to view this ECG Video (17 minutes).
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Dr. Ken Grauer - ECG Video-1 (Blog #95) - Is there AV Block? (August 16, 2014)

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     This is the 1st installment of my ECG Video Blog. The case illustrates important points regarding what does and does not constitute AV block. Please Give Me Feedback (ekgpress@mac.com) as to whether you like this new Video format — which I hope to use more to enhance my ECG Blog.
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NOTE: There are advantages to using a video format format. These include:
  • Ability to illustrate concepts not done full justice by the written word.
  • Greater dispersion of my content through Google & YouTube. This material is free for anyone to use.
-----------------------------------------
LINK to my ECG Video-Blogs and other ECG Resources (including Power Point Shows of my video blogs):
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Acknowledgments — My appreciation to the following individuals:
  • Mike Frease — for providing me with the case for ECG Audio-Blog #1.
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Interpret the simultaneously-recorded 2-lead rhythm strip shown in Figure-1.
  • Is AV block present on this tracing? IF so — What kind of AV block?
  • Is there enough information to know for certain?
  • How does one distinguish AV block from other causes of relative pauses, such as PACs (blocked or conducted) and/or Sick Sinus Syndrome?
Figure-1: 2-lead rhythm srip. Is there AV block? (Figure reproduced with permission from Mike Frease). NOTE — Enlarge by clicking on Figures — Right-Click to open in a separate window.
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GTO – https://www.youtube.com/watch?v=9xC-Ch9sS5I - on YouTube to view this ECG Video and for the Answer (15 minutes). 
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Sunday, 6 July 2014

Dr. Ken Grauer - ECG Blog #94 - BASICS #7 (July 6, 2014)

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     This is my 7th installment of Basic ECG Concepts. My GOAL is to present concise review of some less advanced topics. This topic reviews assessment of Q-R-S-T Changes in the Systematic Approach  with reference to selected more advanced concepts. Please check this out. As always, your feedback is WELCOME!
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ECG Basics #7Q-R-S-T Changes -


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  • CLICK HERE for Full Discussion on my ECG Blog #94.
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Monday, 23 June 2014

Dr. Ken Grauer - ECG Blog #93 - BASICS #6 (June 23, 2014)

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     This is my 6th installment of Basic ECG Concepts. My GOAL is to present concise review of some less advanced topics. This topic reviews the fundamentals of the Systematic Approach to ECG Interpretation  with reference to selected more advanced concepts. Please check this out. As always, your feedback is WELCOME!
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ECG Basics #6Systematic Approach -

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  • CLICK HERE for Full Discussion on my ECG Blog #93.
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Thursday, 19 June 2014

Dr. Ken Grauer - ECG Blog #92 - BASICS #5 (June 19, 2014)

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     This is my 5th installment of Basic ECG Concepts. My GOAL is to present concise review of some less advanced topics. This topic reviews the fundamentals of the ECG Diagnosis of LVH  with reference to selected more advanced concepts. Please check this out. As always, your feedback is WELCOME!
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ECG Basics #5LVH -


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  • CLICK HERE for Full Discussion on my ECG Blog #92.
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