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13 CASE 13


A 22-year-old female college student comes to the university clinic complaining of palpitations.


The patient has had occasional incidences of rapid heart rates but never lasting for more than 2 minutes. In this instance, the heart rate has been elevated for 15 minutes. The patient has only been sleeping 4 hours a night while studying for examinations and is consuming “more than the usual amount” of coffee to help her remain alert. Her father died of a heart attack 3 years ago at the age of 55.



PHYSICAL EXAMINATION



VS: T 37°C, P 180/min, R 22/min and shallow, BP 95/80 mm Hg

PE: Patient is anxious. Pulse is extremely rapid and regular. No murmurs are present, and the lungs are clear.


LABORATORY STUDIES



ECG: Ventricular tachycardia, characterized by narrow QRS complexes at a rate of 180/min. Atrial P waves are also present at a rate of 180/min, but the QRS complexes precede the P wave.


DIAGNOSIS


Paroxysmal supraventricular tachycardia



PATHOPHYSIOLOGY OF KEY SYMPTOMS


Cardiac depolarization normally begins in the sinoatrial (SA) node, passes through the atria to the atrioventricular (AV) node, and, after a delay, enters the ventricle through the common bundle of His and proceeds through the bundle branches and Purkinje fibers, ultimately reaching the ventricular muscle cells. The AV node is characterized by a slow conduction rate. A slow conduction through the AV node normally allows the atria to finish their contraction before the ventricles begin their period of contraction.


The electrocardiogram provides a record of the flow of current that accompanies depolarization of the heart. The normal electrocardiogram consists of a P wave, representing atrial depolarization, a QRS complex representing ventricular depolarization, and a T wave representing ventricular repolarization. This sequence is termed “normal sinus rhythm.” Spread of the depolarization through the AV node is contained within the PR interval (Fig. 13-1).


image

FIGURE 13–1 Normal electrocardiogram.

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Jul 4, 2016 | Posted by in PHYSIOLOGY | Comments Off on 13

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