Wide-Complex Tachycardia in a Patient Presenting with Chest Pain
A 69-year-old male patient presented to the emergency department with worsening symptoms of congestive heart failure (CHF) and acute onset of chest pain. He had awoken at 3 a.m. the day of admission with nonradiating substernal chest pain of low intensity but associated with acute shortness of breath that was relieved by sitting upright. His medical history included known coronary artery disease (CAD), with a percutaneous coronary intervention and stent placement in the left circumflex artery 18 months previously. He was also status post-aortic valve replacement times two, the most recent being a porcine valve placed in 1986. This prosthetic valve was found to be stenotic and insufficient on echocardiography, which also revealed an estimated ejection fraction of 0.40. Cardiac risk factors included diabetes mellitus, hypertension, and hyperlipidemia. Medications on admission included aspirin, lisinopril, pravastatin, doxazosin, isosorbide mononitrate, and leuprolide acetate (Lupron) for prostate cancer. The patient's physical examination was unremarkable except for an elevated jugular venous pressure (estimated at 10 cm), a positive S3 heart sound, and 1+ edema of the extremities. Chest x-ray showed moderate interstitial edema and a right-sided pleural effusion. Pulmonary embolus was ruled out by spiral computed tomography in the emergency department. The initial troponin I level was <0.3 (negative) and serum electrolytes, blood urea nitrogen, and creatinine were all within normal limits.
Admission vital signs were a temperature of 36.3ºC pulse of 120, respirations of 24, and a cuff blood pressure of 157/83 mm Hg. Oxygen saturation was 99% by pulse oximetry on two liters of O2 per nasal cannula. The initial 12-lead electrocardiogram (EKG) was as follows (Figure 1):
(Enlarge Image)
This 12-lead EKG shows a regular, wide-complex tachycardia that appears to be supraventricular, as there is a small P wave discernible before every QRS complex (note lead II and V1 rhythm strips). The ventricular rate is approximately 120 beats per minute. The QRS waveform is wide, nearly 0.16 seconds in duration, and in a left bundle branch pattern. Comparison to an available previous 12-lead EKG from 18 months previously confirmed that the left bundle branch block was not new, and there was no change in either QRS morphology or an established left axis deviation. Left axis deviation is the deviation of the frontal plane QRS axis (sum of the QRS depolarization vectors) from normal, with the axis located between -30 and -90 degrees. Left bundle branch block is associated with an inherently "abnormal" repolarization pattern that impedes the evaluation of the ST segment for evidence of acute myocardial injury. The previous ("old") EKG is shown for comparison in Figure 2.
(Enlarge Image)
For the time being, the patient remained hemodynamically stable but his continued tachycardia placed an increased oxygen demand on his myocardium in the face of possible impending infarction. Rate control was essential. To clearly confirm the patient's rhythm before treatment, a continuous 12-lead EKG was initiated (Figure 3):
(Enlarge Image)
A 12-mg adenosine i.v. push was administered. The patient's heart rate slowed enough to more clearly reveal two P waves for every QRS complex and the absence of atrioventricular dissociation, confirming a supraventricular rhythm. The unusual P axis indicated an ectopic atrial focus, rather than a sinoatrial node focus. The patient's rhythm was therefore diagnosed as an atrial tachycardia with a 2:1 block (only one of every two P waves conducted to the ventricles; one of these P waves is obscured by the T wave during the more tachycardic period). The transient nature of the patient's heart rate slowing, then quick resumption of a rapid ventricular rate was further indicative of a supraventricular focus, see Figure 4.
(Enlarge Image)
A 69-year-old male patient presented to the emergency department with worsening symptoms of congestive heart failure (CHF) and acute onset of chest pain. He had awoken at 3 a.m. the day of admission with nonradiating substernal chest pain of low intensity but associated with acute shortness of breath that was relieved by sitting upright. His medical history included known coronary artery disease (CAD), with a percutaneous coronary intervention and stent placement in the left circumflex artery 18 months previously. He was also status post-aortic valve replacement times two, the most recent being a porcine valve placed in 1986. This prosthetic valve was found to be stenotic and insufficient on echocardiography, which also revealed an estimated ejection fraction of 0.40. Cardiac risk factors included diabetes mellitus, hypertension, and hyperlipidemia. Medications on admission included aspirin, lisinopril, pravastatin, doxazosin, isosorbide mononitrate, and leuprolide acetate (Lupron) for prostate cancer. The patient's physical examination was unremarkable except for an elevated jugular venous pressure (estimated at 10 cm), a positive S3 heart sound, and 1+ edema of the extremities. Chest x-ray showed moderate interstitial edema and a right-sided pleural effusion. Pulmonary embolus was ruled out by spiral computed tomography in the emergency department. The initial troponin I level was <0.3 (negative) and serum electrolytes, blood urea nitrogen, and creatinine were all within normal limits.
Admission vital signs were a temperature of 36.3ºC pulse of 120, respirations of 24, and a cuff blood pressure of 157/83 mm Hg. Oxygen saturation was 99% by pulse oximetry on two liters of O2 per nasal cannula. The initial 12-lead electrocardiogram (EKG) was as follows (Figure 1):
(Enlarge Image)
This 12-lead EKG shows a regular, wide-complex tachycardia that appears to be supraventricular, as there is a small P wave discernible before every QRS complex (note lead II and V1 rhythm strips). The ventricular rate is approximately 120 beats per minute. The QRS waveform is wide, nearly 0.16 seconds in duration, and in a left bundle branch pattern. Comparison to an available previous 12-lead EKG from 18 months previously confirmed that the left bundle branch block was not new, and there was no change in either QRS morphology or an established left axis deviation. Left axis deviation is the deviation of the frontal plane QRS axis (sum of the QRS depolarization vectors) from normal, with the axis located between -30 and -90 degrees. Left bundle branch block is associated with an inherently "abnormal" repolarization pattern that impedes the evaluation of the ST segment for evidence of acute myocardial injury. The previous ("old") EKG is shown for comparison in Figure 2.
(Enlarge Image)
For the time being, the patient remained hemodynamically stable but his continued tachycardia placed an increased oxygen demand on his myocardium in the face of possible impending infarction. Rate control was essential. To clearly confirm the patient's rhythm before treatment, a continuous 12-lead EKG was initiated (Figure 3):
(Enlarge Image)
A 12-mg adenosine i.v. push was administered. The patient's heart rate slowed enough to more clearly reveal two P waves for every QRS complex and the absence of atrioventricular dissociation, confirming a supraventricular rhythm. The unusual P axis indicated an ectopic atrial focus, rather than a sinoatrial node focus. The patient's rhythm was therefore diagnosed as an atrial tachycardia with a 2:1 block (only one of every two P waves conducted to the ventricles; one of these P waves is obscured by the T wave during the more tachycardic period). The transient nature of the patient's heart rate slowing, then quick resumption of a rapid ventricular rate was further indicative of a supraventricular focus, see Figure 4.
(Enlarge Image)
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