How to Determine Systolic Contraction Amplitudes

Systolic blood pressure extremes are often measured as part of research studies.

"Systolic contraction amplitude" refers to how much arterial pressure variance occurs during the left ventricle's contraction. Systolic blood pressure is the measurement pressure exerted when the heart contracts, while diastolic pressure measures the pressure the heart exerts when relaxed. Amplitude measures the farthest difference between a value and its average value. When physicians measure the systolic contraction amplitude for a patient, they are looking for significant differences between the average systolic blood pressure and, usually, the extreme highs. These numbers can prove useful when researchers want to compare the effectiveness of treatment methods for people who have heart disease.

Things You'll Need

• Echocardiography equipment

Instructions

1. Attach the patient to echocardiography equipment. Echocardiography uses sound waves to obtain a picture of what the heart is doing by bouncing the waves off the tissue and back to a transducer that turns the impulses into the image.

2. Take multiple looping digital images of the heart in action. To measure the systolic contraction amplitude, you need images of the heart from several different perspectives — including the long-axis view, the two-chamber view and the four-chamber view — while it contracts and relaxes.

3. Measure the maximum strain in each segment. The American Society of Echocardiography created a model that divides the left ventricle into 16 segments. Use this model to examine the digital images and approximate the highest amount of strain exerted on each of those segments.

4. Obtain an average of the amplitudes. To calculate the systolic contraction amplitude, you must average the amplitudes for all 16 of those segments. The answer is referred to as the "global systolic contraction amplitude" ("GSCA").

Tips & Warnings

• Although most studies seem to use GSCA calculations to look at maximum strain levels, usually for patients with some type of heart disease, theoretically the same method could look at minimum strain levels as well. While high systolic extremes can cause blood vessel blockages over time, low extremes suggest that insufficient pressure exists to move the blood through the vessels to the cells.

• The 16-segment model of the left ventricle is only one of several models developed to analyze the wall motion of that part of the heart. Other research has suggested using a 17- or 18-segment model. However, in clinical work, the 16-segment model has proven the most practical.

References

• eMedTV; Systolic Blood Pressure; Arthus Schoenstadt; Dec. 5, 2008
• MedicineNet; Defintion of Systolic; April 27, 2011
• Merriam-Webster Dictionary: Amplitude
• Medline Plus; Echocardiogram; May 23, 2011
• Journal of the American College of Cardiology; Tissue Doppler Imaging Predicts Improved Systolic Performance and Reverse left Ventricular Remodeling During Long-Term Cardiac Resynchronization Therapy; Peter Sogaard, Henrik Egeblad, W. Yong Kim, Henrik K. Jensen, et al.; September 11, 2001
• Cardiovascular Ultrasound; Influence of Oxygen Tenstion on Myocardial Performance. Evaluation by Tissue Doppler Imaging; Ole Frobert, Jocab Moesgaard; Egon Toft; Steen H. Poulsen, Peter Sogaard; Aug. 26, 2004
• Echobasics; Systolic LV Function; Derliz Mereles