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CLINICAL RESEARCH: ULTRASOUND IMAGING IN CORONARY DISEASE

Enhanced coronary flow velocity during intra-aortic balloon pumping assessed by transthoracic doppler echocardiography

Masaaki Takeuchi, MD^*,*, Yuichi Nohtomi, MD, Hidetoshi Yoshitani, MD^*, Chinami Miyazaki, MD^*, Kazuo Sakamoto, MD^* and Junichi Yoshikawa, MD

^* Department of Internal Medicine, Tane General Hospital, Osaka, Japan
Department of Cardiology, Iizuka Hospital, Fukuoka, Japan
Department of Internal Medicine and Cardiology, Graduate School of Medicine, Osaka City University, Osaka, Japan

Manuscript received May 7, 2003; revised manuscript received August 6, 2003, accepted August 26, 2003.

^* Reprint requests and correspondence: Dr. Masaaki Takeuchi, Department of Internal Medicine, Tane General Hospital, 1-2-31 Sakaigawa, Nishi-ku, Osaka, 550-0024 Japan.
masaaki_takeuchi{at}hotmail.com

	Abstract

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OBJECTIVES: The study was done to determine potential utility of measuring coronary flow velocity (CFV) by transthoracic Doppler echocardiography (TTDE) during intra-aortic balloon pumping (IABP).

BACKGROUND: Use of IABP has been shown to increase CFV assessed by an invasive technique. The CFV in the left anterior descending coronary artery (LAD) can be measured by TTDE.

METHODS: Coronary flow velocity in the distal LAD by TTDE was measured in 40 critically ill patients requiring IABP. All patients received emergency coronary angiography. Both CFV and pressure data were obtained during 1:2 balloon pumping.

RESULTS: Adequate diastolic CFV recording was obtained in all patients. The IABP decreased systolic pressure and increased diastolic pressure. Average peak diastolic flow velocity and diastolic velocity time integral was 19 ± 11 cm/s and 7.7 ± 4.4 cm with non-augmented beat. These values were increased significantly (61 ± 38%, 59 ± 35%, p < 0.001) with augmented beat. Significant correlation was noted between % diastolic pressure augmentation and % increase in diastolic CFV (r = 0.62 to 0.69, p < 0.001). There was no significant difference in flow enhancement during IABP, irrespective to the proximal LAD stenosis severity (severe stenosis: 73 ± 70%; intermediate stenosis: 61 ± 29%; no significant stenosis: 58 ± 29%; p = NS, analysis of variance). By continuous recording of CFV, the optimal timing of balloon control could be adjusted to maximize flow velocity during augmentation.

CONCLUSIONS: Use of TTDE can be employed in monitoring CFV augmentation during IABP. The IABP produced significant distal flow enhancement even in patients with critical proximal stenosis. This totally noninvasive approach may help to optimize the benefits of IABP for coronary flow augmentation.

Abbreviations and Acronyms   APDV = time-averaged peak diastolic velocity   APSV = time-averaged peak systolic velocity   BP = blood pressure   CFV = coronary flow velocity   DFVI = diastolic flow velocity integral   IABP = intra-aortic balloon pumping   LAD = left anterior descending coronary artery   MI = myocardial infarction   QCA = quantitative coronary angiography   SFVI = systolic flow velocity integral   TIMI = Thrombolysis In Myocardial Infarction   TTDE = transthoracic Doppler echocardiography

We hypothesized that CFV in the distal part of the LAD would be increased by IABP even in patients with critical proximal stenosis. Thus, the purpose of this study was to evaluate 1) noninvasive assessment of coronary hemodynamics using TTDE during IABP; and 2) whether this method can be utilized to adjust the timing of balloon control in critically ill patients.

	Methods

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The study group comprised 40 patients who had placement of an IABP for typical clinical indications. Written informed consent for the placement of IABP and emergency coronary angiography was obtained from the patient, or family, or both before the study. The protocol was approved by the hospital's ethics committee.

Coronary angiography was performed in a routine fashion either after or before insertion of the IABP using the femoral approach with standard Judkins diagnostic catheters. Coronary angioplasty (balloon angioplasty, stent deployment) or thrombolytic therapy was performed when clinically indicated. After completion of the necessary interventions, patients were transferred to the coronary care unit.

Coronary flow velocity recordings.   All data were obtained during 1:2 IABP in the coronary care unit. The intra-aortic balloon inflation was begun at the aortic dicrotic notch, and deflation was set on the R wave with manual inflation and deflation adjustments. The TTDE was performed with a commercially available ultrasound machine (SONOS 5500, Philips Medical Systems, Andover, Massachusetts) with a broadband high-frequency (5 to 12 MHz) transducer (S12). Color Doppler detection of LAD flow was obtained as previously described (11,12). Briefly, the left ventricle was imaged in the low parasternal long axis cross section, and then the ultrasound beam was inclined laterally. Next, coronary blood flow in the distal portion of the LAD was identified as a color-filled tubular structure in the anterior interventricular sulcus under the guidance of Doppler color flow mapping. The long-axis sections were carefully adjusted to minimize the angle between the Doppler beam and the LAD flow. With a sample volume positioned on the color signal in the LAD in diastole, pulsed Doppler signal tracings of flow velocity in the LAD were recorded. Angle correction was performed if the angle between ultrasound beam and coronary flow direction was >20°. The aortic blood pressure (BP) was simultaneously measured for the lumen of the intra-aortic balloon pump through fluid-filled tubing using standard pressure transducers.

Coronary flow velocity measurements.   Phasic coronary flow velocity signals were recorded at 50- and 100-mm/s speed, and measurements were made off-line by use of the built-in calculation package of the ultrasound unit (Fig. 1). The diastolic flow velocity integral (DFVI) was obtained by planimetry of the area under the diastolic velocity signal. The time-averaged peak diastolic flow velocity (APDV) was determined from the traced area of the diastolic flow velocity signal. Deceleration time of diastolic flow velocity was also measured. At least three augmented and three non-augmented beats with adequate quality of coronary flow velocity envelope were measured and averaged in each setting. In addition to the absolute values, coronary flow velocity variables were also reported as a percent of non-augmented beat value calculated as [(CFV variables augmented – CFV variables non-augmented)/CFV variables non-augmented] x 100. In patients who could be recorded, adequate systolic CFV envelope, systolic flow velocity integral (SFVI), and time-averaged peak systolic flow velocity (APSV) were also measured with non-augmented beat and with augmented beat.

View larger version (80K): [in this window] [in a new window]   Figure 1 Coronary flow velocity and pressure recordings demonstrating the effects of intra-aortic balloon pumping. (A) Left panel shows phasic coronary flow velocity during 1:2 balloon pumping in a patient with congestive heart failure and high-risk coronary angioplasty (two-vessel disease). First and third coronary flow velocity (CFV) is with augmented beat, and second and fourth CFV is with non-augmented beat. Diastolic CFV is augmented with balloon pumping. Right panel shows aortic pressure. The diastolic pressure before the balloon pumping is shown at D1. The augmented diastolic pressure was labeled S2. (B) Coronary flow velocity and aortic pressure in a patient with recent anterior MI and left main coronary stenosis plus two-vessel disease. First and third CFV is with augmented beat, and second and fourth CFV is with non-augmented beat. Again, diastolic CFV is enhanced with augmented beat.

Pressure measurements.   Aortic pressure was recorded at 25- and 50-mm/s paper speed. During IABP, the first lowest arterial pressure after the R wave was defined as non-augmented diastolic pressure (D1) (Fig. 1). The augmented diastolic pressure was labeled S2. The percent diastolic pressure augmentation was calculated as [(S2 – D1)/D1] x 100 as previously reported (2,3).

Analysis of coronary angiography.   Percent diameter stenosis in the LAD and left main coronary artery was quantitatively analyzed by Philips quantitative coronary angiography (QCA) DCI-ACA system or the Toshiba QCA system. Contrast flow through in the LAD was graded by standard Thrombolysis In Myocardial Infarction (TIMI) flow scale of 0 to 3 from the final coronary angiogram (13). Patients were classified according to the presence and severity of proximal LAD or left main coronary artery stenosis: severe stenosis (>90%); intermediate stenosis (50% to 90%); and no significant stenosis (<50%).

Observer variability.   Interobserver measurement variability was determined by independent measurement on the same CFV recording, and by measurement on the independent CFV recording in eight randomly selected patients. Intraobserver variability was determined by having one observer remeasure the spectral envelopes in eight patients one month apart. Interobserver and intraobserver variabilities were calculated as the SD of the differences between two measurements and expressed as a percent of the average value.

Statistical analysis.   Data are expressed as mean ± SD. Each patient served as his or her own control by using the non-augmented data as the baseline value. The difference of CFV and pressure data between non-augmented beats and augmented beats was evaluated by the paired Student t test. Comparisons of continuous variables among three groups were made by analysis of variance (ANOVA). Linear regression analysis was applied to estimate the relation between pressure data and percent diastolic CFV changes. Statistical differences were considered significant at a value of p < 0.05.

	Results

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Study patients.   Twenty-six patients had acute MIs, including 17 anterior, 5 inferior, and 4 lateral infarctions (Table 1). Three patients required IABP for high-risk coronary angioplasty, and four patients had unstable angina with multivessel disease. One patient had intractable ventricular fibrillations after recent MI. Six other patients had cardiogenic shock, due to acute myocarditis in two, dilated cardiomyopathy in two, and ischemic cardiomyopathy in two patients, respectively. Coronary artery disease was generally extensive, and eight patients had significant left main coronary stenosis. Final coronary angiography showed severe proximal LAD or left main stenosis (>90%) in seven patients, intermediate stenosis (50% to 90%) in 11, and no significant stenosis (<50%) in 22 patients, respectively. Seven patients had received emergency or elective coronary bypass surgery after the coronary angiography. Four patients died of intractable congestive heart failure and hypotension.

Systemic hemodynamics.   All patients had sinus rhythm with a mean heart rate of 87 ± 19 beats/min (range 58 to 124 beats/min) during acquisition of data. Seven patients had baseline systolic BP <90 mm Hg. Intra-aortic balloon pumping decreased systolic BP from 105 ± 19 mm Hg with non-augmented beat to 95 ± 19 mm Hg with augmented beat (p < 0.001). Diastolic BP (61 ± 13 mm Hg) was augmented to 118 ± 18 mm Hg (p < 0.001), an average increase of 105 ± 70% (range 38% to 440%).

Coronary flow velocity.   Adequate quality of diastolic coronary flow velocity envelope was obtained in all patients (Table 2). The mean value of diastolic deceleration time was 734 ± 520 ms (range 69 to 2,430 ms). The APDV with non-augmented beat was 19.2 ± 10.5 cm/s, and IABP significantly increased APDV to 30.0 ± 15.9 cm/s (% increase: 61 ± 38%, p < 0.001). The DFVI during balloon pumping was also increased 59 ± 35% over DFVI with non-augmented beat (from 7.7 ± 4.4 cm to 12.1 ± 7.5 cm, p < 0.001). Although there was no significant correlation between baseline systolic BP and percent increase in APDV (r = 0.11, p = NS) or percent increase in DFVI (r = 0.12, p = NS), significant correlation was noted between percent diastolic pressure augmentation and percent increase in APDV (r = 0.69, p < 0.001); and that in DFVI (r = 0.62, p < 0.001). Adequate quality of systolic coronary flow velocity envelope was obtained in 26 of 40 patients. There was no significant difference of APSV (3.7 ± 11.7 cm/s vs. 3.0 ± 11.9 cm/s) and SFVI (1.4 ± 2.1 cm vs. 1.3 ± 2.2 cm) between non-augmented beat and augmented beat.

View larger version (13K): [in this window] [in a new window]   Figure 2 Effect of balloon pumping on coronary flow velocity among three groups according to the severity of proximal stenosis. APDV = time-averaged peak diastolic velocity (cm/s); DFVI = diastolic flow velocity integral (cm); IABP% = percent increase intra-aortic balloon pumping. Shaded bars = no significant stenosis; black bars = intermediate stenosis; open bars = severe stenosis.

Effect of balloon timing on CFV.   Optimal balloon inflation was achieved to adjust diastolic flow augmentation to coincide with upstroke of diastolic acceleration flow (Fig. 3B, arrow). Delayed balloon inflation significantly decreased APDV (42.7 ± 14.8 cm/s vs. 37.9 ± 13.4 cm/s, p < 0.001) and DFVI (16.2 ± 6.1 cm vs. 13.8 ± 5.0 cm, p < 0.001) (Fig. 4). Although D1 did not change (64.4 ± 9.1 mm Hg vs. 64.8 ± 10.6 mm Hg), S2 also significantly decreased (122.2 ± 16.6 mm Hg vs. 110.2 ± 14.6 mm Hg, p < 0.05). Early balloon deflation also significantly decreased APDV (42.1 ± 18.3 cm/s vs. 36.6 ± 16.1 cm/s, p < 0.05) and DFVI (17.6 ± 7.5 cm vs. 14.2 ± 5.3 cm, p < 0.05). However, there was no difference of D1 (64.8 ± 11.6 mm Hg vs. 64.6 ± 12.4 mm Hg, p = NS) and S2 (130.2 ± 10.1 mm Hg vs. 121.3 ± 8.5 mm Hg, p < 0.1).

View larger version (60K): [in this window] [in a new window]   Figure 3 Adjustment of balloon timing during coronary flow velocity recording. Coronary flow velocity during 1:2 balloon pumping in a patient with high-risk percutaneous transluminal coronary angioplasty. Upper panel shows coronary flow velocity and lower panel shows aortic blood pressure. (A) Delayed inflation; there is a notch between diastolic deceleration flow and augmentation flow (arrow). (B) Optimal timing of balloon control; diastolic flow augmentation coincides with the upstroke of diastolic acceleration flow velocity (arrow). (C) Early deflation; flow velocity is terminated early before the R- wave on electrocardiogram (arrows).

View larger version (18K): [in this window] [in a new window]   Figure 4 Individual value of coronary flow velocity during adjustment of the timing of balloon control. Abbreviations as in Figure 2.

	Discussion

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This study demonstrates that the measurement of diastolic CFV in the distal part of the LAD by TTDE during IABP was highly feasible and that diastolic CFV was increased significantly with augmented diastolic pressure during IABP, even in patients with critical proximal stenosis. Diastolic CFV in the distal LAD was also augmented by IABP in patients with reperfused anterior MI and no-reflow phenomenon. These results directly support the potential for augmenting myocardial perfusion during balloon pumping. We also demonstrated that optimal balloon timing on coronary flow augmentation could be adjusted under the guidance of CFV recording by TTDE. Thus, TTDE is useful for non-invasive assessment of coronary hemodynamics during IABP.

Previous studies.   Controversy exists regarding the ability of IABP to increase coronary blood flow in patients who are critically ill or who have significant atherosclerotic coronary stenosis (1–4,6). Although previous studies demonstrated significantly augmented CFV in the proximal LAD by transesophageal echocardiography (6) or augmented CFV in the proximal coronary arteries by Doppler catheters (2), those studies did not address distal flow response in the presence of obstructive coronary narrowings. Subsequently, Kern et al. (3) used Doppler-tipped angioplasty guide wire for measuring CFV distal to the stenosis during IABP and demonstrated a limited distal flow velocity and a failure to increase flow beyond the most critical coronary stenosis. After relief of vessel occlusion or severe coronary stenosis by angioplasty, a 25% augmentation of distal mean CFV and a 35% increase in distal diastolic velocity integral was observed by IABP. However, the advancement of Doppler guide wire itself across the severe stenosis could impede distal coronary blood flow and adversely affect flow measurements.

Current study.   To our best knowledge, this is the first study to examine the effect of IABP on CFV in the distal LAD by TTDE. Adequate quality of diastolic CFV envelope in the distal LAD was obtained in all patients, and a 60% augmentation of distal CFV by balloon pumping was observed. In contrast to the results of previous studies. IABP produced significant distal flow enhancement even in patients with critical proximal LAD stenosis.

Diastolic aortic pressure is a well-known determinant of coronary flow; thus, an increase in the diastolic pressure induced by IABP will have a significant impact on coronary flow augmentation (6). The significant correlation between percent diastolic pressure augmentation and percent increase in diastolic CFV in this study was in agreement with previous studies (2,6). Although we did not measure coronary pressure at the site of CFV recording, these findings suggest that autoregulation of CFV was lost or out of range in the critically ill, and the change in the CFV depends on the degree of distal perfusion pressure.

Patients who experience no-reflow phenomenon after MI have an increased risk of poor left ventricular function and prognosis (17–19). The CFV pattern of no-reflow phenomenon in patients with reperfused acute MI is characterized by the appearance of systolic retrograde flow and rapid deceleration slope of diastolic flow by use of a Doppler guide wire (13–15). In patients with reperfused acute anterior MI, we demonstrated that the degree of diastolic CFV enhancement by IABP was comparable between patients with systolic retrograde flow/rapid deceleration slope and those without. There was no significant difference of systolic flow velocity between the non-augmented beat and the augmented beat in patients with systolic retrograde flow. These results suggest that in addition to pharmacologic interventions (20,21). IABP is an effective therapeutic strategy to enhance CFV in no-reflow phenomenon.

This study also showed that the degree of the increase in CFV by IABP depends on the timing of balloon inflation and deflation, and TTDE allows adjusting the optimal timing of balloon control for maximal CFV enhancement. This is another advantage of noninvasive monitoring of CFV during balloon pumping.

Study limitations.   Flow velocity measurements do not provide an absolute value but are linearly related to changes in absolute flow when vessel area remains constant. Although we did not measure coronary vessel diameter, unchanged diameter during balloon pumping was reported in a previous study (3).

Coronary flow velocity measurements were not performed before the interventional therapy but were performed after the patients were admitted to the coronary care unit. Thus, we cannot guarantee whether the same results would be obtained before coronary intervention in the cardiac catheterization laboratory.

It was only in two-thirds of the study patients that an adequate quality systolic flow velocity envelope could be recorded, because of the movement of coronary vessels during cardiac cycle and wall motion artifact. However, diastolic flow is dominant in this part of the epicardial coronary artery. The finding that no significant change in systolic flow velocity between non-augmented beat and augmented beat was observed in this study, especially in patients with systolic retrograde flow, suggests that systolic flow velocity has only a small impact on coronary flow augmentation during IABP.

Conclusions.   Transthoracic Doppler echocardiography can be used in monitoring CFV augmentation during IABP. In contrast to previous invasive studies, IABP produced significant distal flow enhancement even in patients with critical proximal stenosis. This totally noninvasive approach may help to optimize the benefits of IABP for coronary flow augmentation.

	References

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1. Katz ES, Tunick PA, Kronzon I. Observations of coronary flow augmentation and balloon function during intraaortic balloon counterpulsation using transesophageal echocardiography. Am J Cardiol. 1992;69:1635–1639[CrossRef][Medline]
2. Kern MJ, Aguirre FV, Tatineni S, et al. Enhanced coronary blood flow velocity during intraaortic balloon counterpulsation in critically ill patients. J Am Coll Cardiol. 1993;21:359–368[Abstract]
3. Kern MJ, Aguirre F, Bach R, Donohue T, Siegel R, Segal J. Augmentation of coronary blood flow by intra-aortic balloon pumping in patients after coronary angioplasty. Circulation. 1993;87:500–511[Abstract/Free Full Text]
4. Port SC, Patel S, Schmidt DH. Effects of intraaortic balloon counterpulsation on myocardial blood flow in patients with severe coronary artery disease. J Am Coll Cardiol. 1984;3:1367–1374[Abstract]
5. Ryan EW, Foster E. Images in cardiovascular medicine. Augmentation of coronary blood flow with intra-aortic balloon pump counter-pulsation. Circulation. 2000;102:364–365[Free Full Text]
6. Zehetgruber M, Mundigler G, Christ G, et al. Relation of hemodynamic variables to augmentation of left anterior descending coronary flow by intraaortic balloon pulsation in coronary artery disease. Am J Cardiol. 1997;80:951–955[CrossRef][Medline]
7. Caiati C, Montaldo C, Zedda N, Bina A, Iliceto S. New noninvasive method for coronary flow reserve assessment: contrast-enhanced transthoracic second harmonic echo Doppler. Circulation. 1999;99:771–778[Abstract/Free Full Text]
8. Caiati C, Zedda N, Montaldo C, Montisci R, Iliceto S. Contrast-enhanced transthoracic second harmonic echo Doppler with adenosine: a noninvasive, rapid and effective method for coronary flow reserve assessment. J Am Coll Cardiol. 1999;34:122–130[Abstract/Free Full Text]
9. Daimon M, Watanabe H, Yamagishi H, et al. Physiologic assessment of coronary artery stenosis by coronary flow reserve measurements with transthoracic Doppler echocardiography: comparison with exercise thallium-201 single piston emission computed tomography. J Am Coll Cardiol. 2001;37:1310–1315[Abstract/Free Full Text]
10. Hozumi T, Yoshida K, Ogata Y, et al. Noninvasive assessment of significant left anterior descending coronary artery stenosis by coronary flow velocity reserve with transthoracic color Doppler echocardiography. Circulation. 1998;97:1557–1562[Abstract/Free Full Text]
11. Takeuchi M, Miyazaki C, Yoshitani H, Otani S, Sakamoto K, Yoshikawa J. Assessment of coronary flow velocity with transthoracic Doppler echocardiography during dobutamine stress echocardiography. J Am Coll Cardiol. 2001;38:117–123[Abstract/Free Full Text]
12. Takeuchi M, Yoshitani H, Miyazaki C, Otani S, Sakamoto K, Yoshikawa J. Relation between changes in coronary flow velocity and in wall motion for assessing contractile reserve during dobutamine stress echocardiography. J Am Soc Echocardiogr. 2002;15:1290–1296[CrossRef][Medline]
13. Kawamoto T, Yoshida K, Akasaka T, et al. Can coronary blood flow velocity pattern after primary percutaneous transluminal coronary angioplasty [correction of angiography] predict recovery of regional left ventricular function in patients with acute myocardial infarction? Circulation. 1999;100:339–345[Abstract/Free Full Text]
14. Iwakura K, Ito H, Takiuchi S, et al. Alternation in the coronary blood flow velocity pattern in patients with no-reflow and reperfused acute myocardial infarction. Circulation. 1996;94:1269–1275[Abstract/Free Full Text]
15. Iwakura K, Ito H, Nishikawa N, et al. Early temporal changes in coronary flow velocity patterns in patients with acute myocardial infarction demonstrating the "no-reflow" phenomenon. Am J Cardiol. 1999;84:415–419[CrossRef][Medline]
16. Shintani Y, Ito H, Iwakura K, et al. Prediction of wall motion recovery from the left anterior descending coronary artery velocity pattern recorded by transthoracic Doppler echocardiography in patients with anterior wall myocardial infarction retrospective and prospective studies. Jpn Circ J. 2001;65:717–722[CrossRef][Medline]
17. Ito H, Tomooka T, Sakai N, et al. Lack of myocardial perfusion immediately after successful thrombolysis. A predictor of poor recovery of left ventricular function in anterior myocardial infarction. Circulation. 1992;85:1699–1705[Abstract/Free Full Text]
18. Ito H, Maruyama A, Iwakura K, et al. Clinical implications of the ‘no reflow’ phenomenon. A predictor of complications and left ventricular remodeling in reperfused anterior wall myocardial infarction. Circulation. 1996;93:223–228[Abstract/Free Full Text]
19. Morishima I, Sone T, Okumura K, et al. Angiographic no-reflow phenomenon as a predictor of adverse long-term outcome in patients treated with percutaneous transluminal coronary angioplasty for first acute myocardial infarction. J Am Coll Cardiol. 2000;36:1202–1209[Abstract/Free Full Text]
20. Ito H, Taniyama Y, Iwakura K, et al. Intravenous nicorandil can preserve microvascular integrity and myocardial viability in patients with reperfused anterior wall myocardial infarction. J Am Coll Cardiol. 1999;33:654–660[Abstract/Free Full Text]
21. Taniyama Y, Ito H, Iwakura K, et al. Beneficial effect of intracoronary verapamil on microvascular and myocardial salvage in patients with acute myocardial infarction. J Am Coll Cardiol. 1997;30:1193–1199[Abstract]

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