Cardiologic Tracings: AT HEART, part #1

CURRENT CONTENTS:
Arteriopath
Atrial fibrillation
Atrial flutter

Bypass grafts
Dipyridamole (stress)
Dobutamine (stress)

Heart block

Holter monitor
(for continuation, see the link below)

Authors' Note: Atrial fib, also abbreviated to a-fib or AF, is medical jargon for atrial fibrillation. Causes for AF include various heart and lung conditions, particularly valvular heart disease, but half of cases occur spontaneously.

AF may be symptomatic or not, and may be intermittent rather than sustained, particularly in its earlier phase. In any case, it is associated with the formation of clots in the atria of the heart, leading to an increased risk of brain stroke, caused by emboli.

To reduce the risk of stroke, patients with AF may be asked to take blood thinners for life. 

Learn more about atrial fibrillation and its treatment at Wikipedia.

Authors' Note: Diagnosis and treatment of atrial arrhythmias, as discussed here, is the field of endeavour of a subgroup of cardiologists. Atrial flutter is readily diagnosed by a pattern on the electrocardiogram distinguished by atrial complexes at a rate of about 300 per minute, with relative block at the atrio-ventricular node resulting in a regular but fast ventricular rate, and pulse, of about 150. Although atrial flutter is not commonly caused by coronary artery disease, it is unlikely that any cardiologist would advocate ad libitum consumption of foods 'loaded with butter'.

Atrial fibrillation, a related cardiac arrhythmia associated with a highly variant heart rate, is discussed above.

Authors' Note: 

 (dye-puh-RIH-duh-mawl)

(Puhr-SANT-in)

Tests of myocardial flow in the Nuclear laboratory, e.g. gated SPECT, require a stimulus so that the specific radiotracer can be injected at peak blood flow to image the state of heart muscle. Ideally, exercise stress, as with a submaximal treadmill procedure, provides this stimulus, with a high attained heart rate reflecting success. As a backup in those unable to exercise sufficiently, (musculoskeletal or breathing problems, reduced fitness), pharmacologic stress may be used. Dipyridamole, tradename Persantine, is a commonly used agent for this purpose, increasing blood flow optimally, but with little change in heart rate or blood pressure. 

Authors' Note:   The verse above is a companion verse to ”dipyridamole”. 

When doctors want to check whether all areas of heart muscle can increase their blood flow appropriately, they may use certain drugs as helpers; this is particularly true when the patient is unable to perform a submaximal exercise test, often called a Bruce treadmill test, after its inventor. Dobutamine (doh-BYOO-ta-meen), relative of adrenaline, raises heart rate and blood pressure. It's the only drug available for tests which use echocardiography to picture the heart while it is 'under stress', but is a second-choice drug for the nuclear imaging test called gated SPECT. The preferred drug for those tests is one whose primary effect is to dilate arterial blood vessels, increasing the flow to normal heart muscle. Such drugs include dipyridamole and adenosine.

Authors' Note:  In disease states, including those producing congestive heart failure, the ejection fraction of the left ventricle, a measure indicating the strength of contraction, provides important information concerning prognosis (potential outcome) and the need for treatment. 

   The ejection fraction can be measured by echocardiography, magnetic resonance imaging, or several different nuclear (radio-isotope) techniques. These techniques measure the volume of the ventricle at the end of diastolic (relaxation) and systolic (contraction) phases of the cardiac cycle. Despite the name, the change during systole is generally given in medical jargon as the percent relative change, rather than as a true fraction; e.g. 60% is good, 30% is bad.

If you have had fun with these verses and are not concerned re their pro-arrhythmogenic effect, you could venture to review the second collection of this type; click HERE for part #2. 

 

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