AACN News—September 2001—Practice
Vol. 18, No. 9, SEPTEMBER 2001
Practice Resource Network: Frequently Asked Questions|
Q:What is the standard of practice for “a” and “v” wave analysis in RA/CVP [right atrium/central venous pressure] and PAWP [pulmonary artery wedge pressure] recordings? Must the recording be run simultaneously with an ECG recording and, if so, why?
A:The “a” and “v” waves of the pulmonary artery (PA) pressure waveform represent the pressure changes in the atria during atrial contraction. Because of the dire complications they may indicate, accurate analysis of each of these waveforms is essential during the ongoing monitoring of critically ill patients.
Elevation of the “a” wave in an RA/CVP waveform can occur as a result of tricuspid stenosis, right ventricular ischemia or failure, pulmonary hypertension, pulmonic stenosis, or atrioventricular dissociation with loss of synchrony. An elevated “a” wave in the PAWP waveform, which is due to resistance to left ventricular filling, can result from mitral stenosis or acute left ventricular ischemia and atrioventricular dissociation, with loss of synchrony.
An abnormal elevation in the “v” wave can occur in the RA/CVP waveform because of tricuspid regurgitation, atrial fibrillation, right ventricular failure with ventricular dilatation, ventricular septal defect, or a noncompliant right atrium. Elevated “v” waves in the PAWP waveform may be due to mitral regurgitation, atrial fibrillation, left ventricular failure and ventricular dilatation, rupture of a papillary muscle after a myocardial infarction, a ventricular septal defect, or a noncompliant left atrium. Abnormal elevation of both the “a” and “v” waves occurs in cases of cardiac tamponade, constrictive pericardial disease, and hypervolemia.
Although the importance of accurate atrial waveform analysis is apparent, the “a” and “v” waves are frequently identical in their amplitude and morphology and difficult to differentiate from each other on an RA/CVP or PAWP recording. The ECG tracing must be used as a reference point. The necessity of the ECG tracing is illustrated when the relationship of the waveforms to heart activity is considered. When the atrial waveform is recorded simultaneously with the ECG recording, the “a” wave on the atrial tracing is preceded slightly by the P wave on the ECG recording. Thus, the a wave reflects the small increase in pressure that precedes atrial contraction. Similarly, the upstroke of the “v” wave reflects the inflow of blood against the closed atrioventricular valves during atrial filling and closely follows the QRS complex on the ECG recording. The crest of the “v” wave represents the opening of the atrioventricular valves and coincides with the ECG’s T wave, and the down slope of the “v” wave is indicative of atrial emptying.
Accurate analysis of the “a” wave in an RA/CVP recording is accomplished by aligning the “a” wave with the PR interval on the ECG tracing. Similarly, the “a” wave on the PAWP recording should be aligned with the end of the QRS complex on the ECG tracing.
Elevation in the “v” wave on RA/CVP and PAWP tracings is most accurately detected by aligning the “v” wave with the simultaneously recorded TP interval on the ECG tracing. RA/CVP “v” waves will be closer to the T wave, whereas PAWP “v” waves will be closer to the P wave. This approach allows differentiation between the a and “v” waves and detection of abnormally elevated waves.
Because large elevations in the “v” wave of a PAWP tracing may resemble a PA (pulmonary artery) waveform, an abnormally elevated “v” wave can easily be mistaken for a normal PA waveform. This is a critical error and could result in permanent “wedging” of the PA catheter in the pulmonary vasculature, causing either a pulmonary infarct and/or rupture. Correlating the “v” wave with the ECG tracing enhances recognition of the abnormal “v” waveform and helps to avoid this serious complication.
Finally, when obtaining RA/CVP or PAWP readings, remember to use the mean of the “a” wave when measuring pressures in the presence of large “v” waves. Including these elevated “v” waves in the measurement of RA/CVP or PAWP will result in erroneously high values.
AACN’s “Protocols for Practice: Hemodynamic Monitoring Series” is a good resource for additional information. To obtain this series, call (800) 899-2226 or visit the online Bookstore at
http://www.aacn.org. Request Item #CC170700. The price is $42 for members ($54 for nonmembers).
Chulay M, Gawlinski A. Protocols for Practice: Hemodynamic Monitoring Series. Aliso Viejo, Calif: American Association of Critical-Care Nurses; 1998:20-21.
Darovic G. Hemodynamic Monitoring: Invasive and Noninvasive Clinical Application. Philadelphia, Pa: WB Saunders Co; 1995:91-92.
Apply for a Critical Care Nursing Research Grant
AACN awards several grants to fund studies that are relevant to critical care nursing practice. The deadlines to apply for some of these grants are approaching. Read on for more information about these grants:
Due Oct. 1, 2001
Evidence-Based Clinical Practice Grant
This grant funds up to $1,000 to stimulate the use of patient-focused data or previously generated research findings to develop, implement and evaluate changes in acute and critical care nursing practice. Eligible projects may include research utilization, CQI or outcomes evaluation. Interdisciplinary and collaborative projects are encouraged.
AACN Clinical Practice Grant
This grant awards $6,000 to support research that focuses on one or more of AACN’s research priorities.
AACN-Sigma Theta Tau Critical Care Grant
Cosponsored by AACN and the Honor Society of Nursing, Sigma Theta Tau International, this grant awards up to $10,000. Applicants must be members of either AACN or Sigma Theta Tau.
Due Jan. 15, 2002
AACN Clinical Inquiry Grant
This grant awards up to $500 to support research that focuses on one or more of AACN’s research priorities. Funds may be applied to new projects or projects in progress. Interdisciplinary projects are especially invited.
Due Feb. 1, 2002
AACN Datex-Ohmeda Nutritional Assessment Grant
This grant funds up to $5,000 to support research related to nutritional assessment of the critically ill patient. Suggested topics include the impact of continuous metabolic monitoring, assessment of the nutritional and metabolic condition, current practices of nutritional assessment, use of the Harris-Benedict Equation vs. indirect calorimetry in nutritional assessment, and evaluation of the accuracy or efficacy of continuous metabolic monitoring.
AACN Certification Corporation Research Grant
This grant awards up to $10,000 for up to four studies related to certified practice. Examples of eligible projects are studies that focus on continued competency, the Synergy Model, the value of certification as it relates to patient care or nursing practice and credentialing concepts.
AACN Critical Care Grant
This grant awards up to $15,000 to support research that focuses on one or more of AACN’s research priorities.
AACN Mentorship Grant
This grant awards up to $10,000 to provide support for a novice researcher, who will be directed by a mentor experienced in the area of proposed investigation.
To obtain grant application materials, call (800) 899-2226 and request Item #1013, or visit the “Clinical Practice” area of the AACN Web site at
AACN Lends Support to AP Nursing Listserv
AACN has provided a $2,500, unrestricted grant to help support the Advanced Nursing Practice in Acute and Critical Care (ANPACC) listserv. The funds will be used to help with ongoing maintenance, yearly subscription fees and additional hardware and software.
Mary McKinley, RN, MSN, CCRN, chair of the 2000-01 Advanced Practice Work Group, represented AACN in presenting a check for the funds to listserv owner Judy Verger, RN, MSN, CCRN, at the Advanced Practice Institute reception in May 2001.
This listserv project supports discussion related to issues for advanced practice nurses, including clinical practice and patient care problems, research utilization, role and scope of practice issues, credentialing and certification. The listserv currently averages approximately 125 messages per month.
The listserv can be accessed via the AACN Web site at
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