A Nervous System Problem–Potential Competing Electric Signals
We used to say that the human being is comprised of two distinct neural systems, one under control of a master executive component called the “central nervous system,” and the other (the “peripheral nervous system”) under an ancillary controller connecting to that executive. In that classical neurology model, the CNS collected and processed information collected from the PNS. As our knowledge of the nervous system has grown, we have come to understand that processing of information and initiation of change in the human organism is managed by a variety of “control subsystems.” Some organs contain their own “servo units” for controlling organ activity. CNS control, PNS control, and a host of subsystems interact to allow our human organism to function. CNS and PNS metabolic controls may influence those subsystems.
Atrial Fibrillation Diagnosis
Normal Heart Function—Just One Complex Servo Subsystem
The heart is a complex servo mechanism loosely connected to both the CNS and PNS. Its muscles are stimulated by a self-initiated electrical impulse 60 to 100 times each minute in the sinoatrical node in the right portion of the heart’s atrium. The nerve impulse proceeds through the atria, triggering a contraction of those muscles, allowing blood to enter the ventricles. These impulses continue and approach the atrioventricular node, slowing slightly to permit the ventricles to complete blood accumulation, and then trigger the ventricles to contract, moving blood to the lungs and other organs. With the pumping contraction completed, a new impulse is generated in that sinoatrical node. A normal heart beat is a serial activity, impulses triggering the top of the heart to contract and then triggering the lower part of to pulse slightly later.
Atrial Fibrillation—A Timing Dysfunction
There are subsystems throughout the body that generate electrical activity, receiving it, altering it, or initiating additional electrical activity. With atrial fibrillation, the cells that generate that initial impulse to the heart’s muscles may not work properly. Pulmonary veins lying near the atria can initiate their own nerve impulse, overpowering or supplanting the normal triggering system for the heart beat. The substitute signal enters the nervous system tract for the heart beating sequence, but the signal appears disorganized to the heart, causing the heart to fibrillate, i.e., causing its beating to misfire and confusing the heart muscles of the proper upper and lower chambers firing order. The whole beating rhythm may result in a 100 to 175 beats per minute with sequencing of the beating out of sync. Blood will still flow from the upper to the lower chambers, but the sequencing mismatch precludes normal flows of blood to the body and may cause fluid build-up in bodily tissues, blood-clotting, etc.
Diagnosing Atrial Fibrillation
At initial physical examination, the physician will ask questions relating to heart palpitations, dizziness, chemical dependency, chest pain, personal and family history of heart disease, blood pressure problems, metabolic disease, breathing problems, familial atrial fibrillation, etc. Baseline heart rate, blood pressure, lung function, and metabolic studies (“blood work”) will be established. Actual heart electrical activity will be delineated by an electrocardiogram (ECG), Holter 24-hour monitor, stress testing that places different work loads on the heart, echocardiogram, chest xray, etc.—all to zero in on the location or site of the abnormal heart electrical activity. Ultimate treatment plan will be based on “localizing” the electrical misfiring lesion site.
