We're unable to sign you in at this time. Please try again in a few minutes.
We were able to sign you in, but your subscription(s) could not be found. Please try again in a few minutes.
There may be a problem with your account. Please contact the AMA Service Center to resolve this issue.
Contact the AMA Service Center:
Telephone: 1 (800) 262-2350 or 1 (312) 670-7827  *   Email: subscriptions@jamanetwork.com
Error Message ......
Article |

Serum Potassium Levels and Myocardial Threshold of Excitability

Weldon J. Walker, MD
JAMA. 1974;228(13):1638. doi:10.1001/jama.1974.03230380016009.
Text Size: A A A
Published online


To the Editor.—  The electrocardiographic tracings or the title must be mislabeled in the article, "Transvenous Pacemaker Failure Induced by Hyperkalemia," by O'Reilly, Murnaghan, and Williams (228:336, 1974), since the tracings show the pacemaker functioning best at highest potassium levels. The text is also confusing. The patient's pacemaker functioned intermittently, regardless of serum potassium levels and the use of numerous agents known to alter myocardial threshold, until it was removed. The removed pacemaker tested as normal. A replacement pacemaker also functioned intermittently. This patient apparently had such extensive endocardial fibrosis as to largely insulate the myocardium from a normal transvenous electrode. Hence, it was a poor case from which to draw conclusions concerning factors influencing myocardial excitability, and the authors' conclusions were contrary to those of most investigators.Siebens et al1 in 1953 demonstrated in dogs a parallel increase of myocardial responsiveness by increasing extracellular potassium levels from 3


Sign in

Purchase Options

• Buy this article
• Subscribe to the journal
• Rent this article ?




Also Meets CME requirements for:
Browse CME for all U.S. States
Accreditation Information
The American Medical Association is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians. The AMA designates this journal-based CME activity for a maximum of 1 AMA PRA Category 1 CreditTM per course. Physicians should claim only the credit commensurate with the extent of their participation in the activity. Physicians who complete the CME course and score at least 80% correct on the quiz are eligible for AMA PRA Category 1 CreditTM.
Note: You must get at least of the answers correct to pass this quiz.
Please click the checkbox indicating that you have read the full article in order to submit your answers.
Your answers have been saved for later.
You have not filled in all the answers to complete this quiz
The following questions were not answered:
Sorry, you have unsuccessfully completed this CME quiz with a score of
The following questions were not answered correctly:
Commitment to Change (optional):
Indicate what change(s) you will implement in your practice, if any, based on this CME course.
Your quiz results:
The filled radio buttons indicate your responses. The preferred responses are highlighted
For CME Course: A Proposed Model for Initial Assessment and Management of Acute Heart Failure Syndromes
Indicate what changes(s) you will implement in your practice, if any, based on this CME course.


Some tools below are only available to our subscribers or users with an online account.

0 Citations

Sign in

Purchase Options

• Buy this article
• Subscribe to the journal
• Rent this article ?

Related Content

Customize your page view by dragging & repositioning the boxes below.