Impaired coronary vasodilator reserve in the immediate postcoronary angioplasty period: analysis of coronary artery flow velocity indexes and regional cardiac venous efflux

Coronary Microvascular Spasm: Clinical Presentation and Diagnosis

Professor Maseri pioneered the research and treatment of coronary vasomotion abnormalities represented by coronary vasospasm and coronary microvascular dysfunction (CMD). These mechanisms can cause myocardial ischaemia even in the absence of obstructive coronary artery disease, and have been appreciated as an important aetiology and therapeutic target with major clinical implications in patients with ischaemia with non-obstructive coronary artery disease (INOCA). Coronary microvascular spasm is one of the key mechanisms responsible for myocardial ischaemia in patients with INOCA. Comprehensive assessment of coronary vasomotor reactivity by invasive functional coronary angiography or interventional diagnostic procedure is recommended to identify the underlying mechanisms of myocardial ischaemia and to tailor the best treatment and management based on the endotype of INOCA. This review highlights the pioneering works of Professor Maseri and contemporary research on coronary vasospasm and CMD with reference to endothelial dysfunction, Rho-kinase activation and inflammation.

Bimodal Pattern of Coronary Microvascular Involvement in Diabetes Mellitus

Background

The contribution of functionally disturbed coronary autoregulation and structurally impaired microvascular vasodilatory function to reduced coronary flow velocity reserve, reflecting impaired coronary microcirculation in diabetes mellitus (DM), has not been clearly elucidated. The objective of this study was to identify the mechanism of coronary microvascular impairment in DM in relation to duration of disease.

Methods and Results

Coronary flow velocities in the anterior descending coronary artery were assessed by transthoracic echocardiography following angiography revealing normal epicardial coronary arteries in 55 diabetic and 47 nondiabetic patients. Average peak flow velocities, coronary flow velocity reserve, and microvascular resistance in baseline and hyperemic conditions (baseline and hyperemic microvascular resistance, respectively) were assessed. Reduced coronary flow velocity reserve in patients with short duration (<10 years) of DM compared with nondiabetic patients was primarily driven by increased baseline average peak flow velocity (26.50±5.6 versus 22.08±4.31, P=0.008) in the presence of decreased baseline microvascular resistance (3.69±0.86 versus 4.34±0.76, P=0.003). In contrast, decreased coronary flow velocity reserve in patients with long‐standing (≥10 years) DM compared with nondiabetic patients was predominantly driven by reduced hyperemic average peak flow velocity (41.57±10.01 versus 53.47±11.8, P<0.001) due to increased hyperemic microvascular resistance (2.13±0.42 versus 1.69±0.39, P<0.001).

Conclusions

Both altered coronary autoregulation and impaired microvascular vasodilatory function contribute to DM‐related coronary microvascular impairment in a time‐dependent manner. DM‐induced early functional microvascular autoregulatory impairment seems to evolve into structural microvascular impairment in the initially overperfused microvascular territory at the later stage of disease.

Role of coronary vasoconstriction in ischemic heart disease and search for novel therapeutic targets

Atherothrombosis has long been recognized as an important mechanism of cardiac events in ischemic heart disease, and large multicenter clinical studies have shown the benefit of antiplatelet agents, statins, beta-blockers and angiotensin converting enzyme inhibitors in preventing these events. However, more recent studies have been less successful at showing incremental gains in targeting these mechanisms, suggesting that the limits of this strategy have been exploited. Coronary vasoconstriction is another important mechanism in ischemic heart disease but has received little attention and yet is a potential therapeutic target. In the current review, the reasons why coronary vasconstriction has received insufficient consideration are explored. In particular, we need to change our approach from lumping heterogeneous clinical entities together to focusing on clinically-discrete homogeneous groups with a common mechanism and thus therapeutic target. The role of coronary vasoconstriction is examined in the various ischemic syndromes (variant angina, chronic stable angina, acute coronary syndromes and syndrome X) and the underlying mechanisms discussed. Finally, in order to advance studies in this field, an innovative research strategy is proposed, including: (1) selection of paradigmatic cases for the various ischemic syndromes; (2) candidate therapeutic targets; and (3) approaches in assessing the clinical efficacy of these potential therapies.

Transthoracic coronary flow reserve and dobutamine derived myocardial function: a 6-month evaluation after successful coronary angioplasty

After percutaneous transluminal coronary angioplasty (PTCA), stress-echocardiography and gated single photon emission computerized tomography (g-SPECT) are usually performed but both tools have technical limitations. The present study evaluated results of PTCA of left anterior descending artery (LAD) six months after PTCA, by combining transthoracic Doppler coronary flow reserve (CFR) and color Tissue Doppler (C-TD) dobutamine stress.

Six months after PTCA of LAD, 24 men, free of angiographic evidence of restenosis, underwent standard Doppler-echocardiography, transthoracic CFR of distal LAD (hyperemic to basal diastolic coronary flow ratio) and C-TD at rest and during dobutamine stress to quantify myocardial systolic (S_m) and diastolic (E_m and A_m, E_m/A_m ratio) peak velocities in middle posterior septum. Patients with myocardial infarction, coronary stenosis of non-LAD territory and heart failure were excluded. According to dipyridamole g-SPECT, 13 patients had normal perfusion and 11 with perfusion defects. The 2 groups were comparable for age, wall motion score index (WMSI) and C-TD at rest. However, patients with perfusion defects had lower CFR (2.11 ± 0.4 versus 2.87 ± 0.6, p < 0.002) and septal S_m at high-dose dobutamine (p < 0.01), with higher WMSI (p < 0.05) and stress-echo positivity of LAD territory in 5/11 patients. In the overall population, CFR was related negatively to high-dobutamine WMSI (r = -0.50, p < 0.01) and positively to high-dobutamine S_m of middle septum (r = 0.55, p < 0.005).

In conclusion, even in absence of epicardial coronary restenosis, stress perfusion imaging reflects a physiologic impairment in coronary microcirculation function whose magnitude is associated with the degree of regional functional impairment detectable by C-TD.

Coronary Flow Reserve after Coronary Intervention is Similar in Patients with Preserved Viability in Previous Myocardial Infarction and in Those with Angina Pectoris

The relationship between coronary flow reserve (CFR) and viability in the infarcted myocardium has not been fully clarified. We measured coronary blood flow velocity immediately after coronary intervention (with percutaneous transluminal coronary angioplasty [PTCA] or stenting) in 38 patients with previous myocardial infarction and preserved viability and 48 with angina pectoris. CFR was calculated and was similar between the two patient groups. No differences in the incidence of post-intervention CFR > 2.0 were detected; there were no differences in postintervention CFR between patients with preserved myocardial viability and those with angina pectoris who underwent PTCA. Coronary stenting reduced the percentage diameter stenosis in both groups compared with PTCA and slightly increased the post-intervention CFR. No differences were, however, detected in postintervention CFR between patients with preserved myocardial viability and those with angina pectoris who underwent additional stenting. These results reveal that in patients with preserved myocardial viability, post-intervention CFR was restored to values similar to those in patients with angina pectoris.

Clinical parameters and functional tests are not predictive for in-stent restenosis

OBJECTIVE

To study the correlation between clinical parameters and the occurrence of in-stent restenosis in a cohort of patients from the Tel Aviv Medical Center who underwent repeat angiograms for clinical indications following stenting.

BACKGROUND

After stenting, recurrences of symptoms or ischemia on functional tests are considered to be clinical signs of restenosis.

METHODS

The authors' study group consisted of 149 out of 1469 patients (10%) who underwent stent implantation between 1996 and 1998 and were under clinical follow-up. This group had a repeat angiogram for clinical indications: chest pain or a positive functional test (thallium study or ergometry).

RESULTS

Sixty-eight patients (45%) had in-stent restenosis (ISR), 32 (21%) had a patent stent site with a significant coronary atherosclerosis elsewhere requiring revascularization (NTLR), and 51 (34%) had a patent stent site and did not require additional revascularization (PS). Baseline characteristics were similar in all the groups. There was a 63% rate of objective evidence of ischemia in the PS group, similar to the ISR (63%) and NTLR (74%) groups. In the ISR versus the NTLR and PS groups the stents were longer (22 +/- 10 versus 17 +/- 7 and 16 +/- 6 mm, p < 0.001) with a smaller diameter (3 +/- 0.4 versus 3.3 +/- 0.5 and 3.2 +/- 0.4 mm, p < 0.05) and a higher rate of multiple stents in the target lesion (34% versus 19% and 14%, p < 0.05)

CONCLUSIONS

In the cohort of patients who underwent angiography following stenting for chest pain or a positive functional test, 55% were found to have a patent stent site. The 5% total in-stent restenosis is significantly lower than the rate in angiography-based reports. On the other hand, the group with a patent stent had a higher than expected rate of objective evidence of ischemia. Therefore clinical parameters and functional tests are not predictive for in-stent restenosis.

[Late recovery of coronary flow reserve in patients successfully treated with a percutaneous procedure]

INTRODUCTION AND OBJECTIVES

Coronary angiograms are of limited value for the assessment of the results of percutaneous interventions. Intracoronary Doppler studies have been used to overcome these difficulties. The achievement of a coronary flow reserve (CFR) > 2-2.5 after the procedure is considered a good result and further optimization is generally not required. However, coronary flow reserve may not recover immediately, despite optimal procedural results. The aim of this study is to assess the temporal course of the recovery of coronary flow reserve after successful revascularization.

PATIENTS AND METHOD

We studied 34 patients with coronary heart disease who were successfully treated by balloon angioplasty (n = 8) or stent implantation (n = 26). In all patients, serial observations were made by quantitative angiography and intracoronary Doppler (0.014 = flow-wire). Patients were studied: a) before treatment; b) immediately after, and c) 8 3 months later.

RESULTS

The baseline coronary flow reserve was 1.3 0.4 and increased to 2.4 0.8 after the procedure (p < 0.01). At 8 months follow-up there was a significant increase (3 0.8; p < 0.01). This late improvement in coronary flow reserve was associated with a decline in average peak velocity at follow-up. Patients with impaired CFR immediately after treatment had a greater increase in CFR during followup than those with CFR > 2 after treatment (1.4 0.9 vs 0.4 0.6; p < 0.01).

CONCLUSIONS

After a successful coronary intervention, CFR increases immediately, but some patients may experience additional improvement during follow-up. This increase was greater in patients who showed less improvement in coronary flow reserve immediately after treatment. Our findings suggest that the use of Doppler parameters in the immediate assessment of percutaneous coronary intervention results have limitations.

Deferring angioplasty in intermediate coronary lesions based on coronary flow criteria is safe: comparison of a deferred group to an intervention group

The decision for revascularization in patients with intermediate coronary lesions remains a challenging topic, particularly when objective data of reversible ischemia are lacking. In some of the patients, coronary revascularization is performed or deferred without definitive evidence on the clinical significance of the coronary stenosis. We investigated the usefulness of coronary flow reserve (CFR) measurements in 28 patients with intermediate coronary lesions. We compared 20 patients who underwent angioplasty based on Doppler-wire-derived CFR with 8 patients for whom angioplasty was deferred (diameter stenosis of 50.7 +/- 2.0% versus 46.5 +/- 3.1%, P < 0.0001 and CFR of 1.80 +/- 0.32 versus 2.65 +/- 0.11, P = 0.002, respectively). Angioplasty resulted in normalization of the CFR to 2.57 +/- 0.53 (P < 0.0001, versus the baseline value). During a follow-up period of 58.1 weeks (range 23-149 weeks), eight patients in the revascularization group were readmitted to the hospital, one of them with a myocardial infarction in the territory of the target vessel, compared with only one admission in the deferred group. Target-vessel revascularization was performed in three patients (a fourth patient declined it) in the former group, compared with only one in the latter. Symptomatic improvement or no change in clinical status was observed in the majority of patients in both groups (90% in the revascularization group and 87.5% in the deferred group). We conclude that in a selected group of patients with intermediate coronary lesions, measurement of CFR may be a useful tool in determining the need for revascularization based on its physiologic significance. Importantly, deferring PTCA in patients with intermediate lesions and normal CFR values seems to be safe.

Early changes in coronary flow physiology after balloon angioplasty or stenting: a 24-hour Doppler flow velocity study

To evaluate early changes in myocardial microcirculation after balloon or stent coronary angioplasty, we studied 57 patients undergoing coronary angioplasty with a Doppler-tipped guidewire, with (n = 26) or without stenting. Postprocedural quantitative coronary angiography and coronary flow velocity were measured after 10 min and 24 hr. As compared to stenting, no stenting was associated with a higher postprocedural stenosis rate (21% +/- 13% vs. 12% +/- 10%; P < 0.05), smaller coronary velocity reserve (CVR; 2.2 +/- 0.4 vs. 2.5 +/- 0.7; P = 0.04), and smaller relative CVR (0.8 +/- 0.2 vs. 1.1 +/- 0.3; P = 0.001). At 24 hr, CVR and relative CVR in the unstented group increased to the level in the stented group, mainly because of a decrease in basal average peak velocity (APV). Overall, there was a significant negative linear relation between CVR and APV variations during the 24-hr period. In the subgroups with persistent abnormalities, CVR variation was closely related to the basal APV/reference APV ratio. In conclusion, coronary reserve normalization can occur within 24 hr after coronary angioplasty and is closely dependent on postangioplasty APV. Myocardial distal resistances should be considered when interpreting postangioplasty CVR.

Coronary hemodynamics of stent implantation after suboptimal and optimal balloon angioplasty

OBJECTIVES

This study was performed to evaluate hemodynamic alterations of stent implantation after Doppler flow-guided balloon angioplasty (BA).

BACKGROUND

There is controversy regarding the effect of stent implantation on coronary hemodynamics after suboptimal and optimal BA.

METHODS

A total of 523 of 620 patients underwent Doppler-guided BA in the setting of a multicenter study and were analyzed before and after additional stent implantation. Balloon angioplasty was considered optimal when the diameter stenosis (DS) was < or = 35% and coronary flow reserve (CFR) was >2.5 and suboptimal if these two criteria were not met. Coronary flow reserve was also measured in an angiographically normal artery to determine relative CFR. Patients were followed for 12 months to document major adverse cardiac events (MACE).

RESULTS

The main difference between patients with suboptimal BA (n = 195 [51%]) and optimal BA (n = 184 [49%]) was a more pronounced increase in baseline blood flow velocity (15 +/- 8 to 22 +/- 11 vs. 14 +/- 8 to 16 +/- 10 cm/s, p < 0.01). Coronary flow reserve improved after stent implantation in both patient groups, owing to a reduction in residual lumen obstruction, as determined by angiographic (%DS) and Doppler flow criteria (hyperemic blood flow velocity, relative CFR), and was associated with a decrease in MACE (16% vs. 7% in optimal BA group, p = 0.08; and 27% vs. 11% in suboptimal BA group, p = 0.007).

CONCLUSIONS

Stent implantation enhances CFR after suboptimal and optimal Doppler-guided BA, owing to a reduction in residual lumen obstruction-determined by angiographical and Doppler flow criteria-as the underlying mechanism for an improved clinical outcome.

Noninvasive assessment of great cardiac vein flow by Doppler echocardiography: a validation study

The objectives of this study were (1) to compare great cardiac vein (GCV) flow velocity detected by pulsed Doppler echocardiography (PDE) with Doppler guide wire (DGW) in the experimental setting and (2) to clarify whether transthoracic Doppler echocardiography (TTDE) can detect GCV flow in humans. Using opened-chest dogs, we detected GCV flow by PDE under the guidance of color flow Doppler mapping. GCV flow velocity was recorded by PDE and DGW, simultaneously. In 23 volunteers, GCV flow velocity was measured by TTDE. In the experimental setting, the prominent systolic flow wave of the GCV was obtained in PDE and DGW. There were good agreements between PDE and DGW for the measurements of GCV flow velocity (peak velocity: r = 0.98, y = 1.12chi-5.9; time velocity integral: r = 0.97, y = 1.10chi-0.71). In the human subjects, clear envelopes of GCV flow velocity were obtained in 21 (91%) of 23 subjects with the use of TTDE.

Assessment of flow velocity reserve by transthoracic Doppler echocardiography and venous adenosine infusion before and after left anterior descending coronary artery stenting

OBJECTIVES

We sought to evaluate whether coronary flow velocity reserve (CFR) (the ratio between hyperemic and baseline peak flow velocity), as measured by transthoracic Doppler echocardiography during adenosine infusion, allows detection of flow changes in the left anterior descending coronary artery (LAD) before and after stenting.

BACKGROUND

The immediate post-stenting evaluation of CFR by intracoronary Doppler has shown mixed results, due to reactive hyperemia and microvascular stunning. Noninvasive coronary Doppler echocardiography may be a more reliable measure than intracoronary Doppler.

METHODS

Transthoracic Doppler echocardiography during 90-s venous adenosine infusion (140 microg/kg body weight per min) was used to measure CFR of the LAD in 45 patients before and 3.7 +/- 2 days after successful stenting, as well as in 25 subjects with an angiographically normal LAD (control group).

RESULTS

Adequate Doppler spectra were obtained in 96% of the patients. Pre-stent CFR was significantly lower in patients than in control subjects (diastolic CFR: 1.45 +/- 0.5 vs. 2.72 +/- 0.71, p < 0.01; systolic CFR: 1.61 +/- 1.02 vs. 2.41 +/- 0.68, p < 0.01) and increased toward the normal range after stenting (diastolic CFR: 2.58 +/- 0.7 vs. 2.72 +/- 0.75, p = NS; systolic CFR: 2.43 +/- 1.01 vs. 2.41 +/- 0.52, p = NS). Diastolic CFR was often damped, suggesting coronary steal in patients with > or =90% versus <90% LAD stenosis (0.86 +/- 0.23 vs. 1.69 +/- 0.43, p < 0.01). Coronary stenting normalized diastolic CFR in these two groups (2.45 +/- 0.77 and 2.64 +/- 0.69, respectively, p = NS), even though impaired diastolic CFR persisted in three of four patients with > or =90% stenosis. Stenosis of the LAD was better discriminated by diastolic (F = 49.30) than systolic (F = 12.20) CFR (both p < 0.01).

CONCLUSIONS

Coronary flow reserve, as measured by transthoracic Doppler echocardiography, is impaired in LAD disease; it may identify patients with > or =90% stenosis; and it normalizes early after stenting, even in patients with > or =90% stenosis.

Serial evaluation of coronary flow reserve by transesophageal doppler echocardiography after angioplasty of proximal left anterior descending coronary artery: a 6-month follow-up study

BACKGROUND

Coronary flow reserve can be estimated by transesophageal Doppler echocardiography (TDE).

OBJECTIVE

To evaluate the coronary flow reserve by TDE, serially over 6 months' follow-up, after successful percutaneous transluminal coronary angioplasty (PTCA) of proximal left anterior descending coronary artery (LADA).

METHODS AND RESULTS

We performed TDE examination of 30 patients (mean age 55 +/- 9 years) 72 h, 3 months, and 6 months after PTCA of LADA. Selective angiography of LADA was repeated 72 h and 6 months after PTCA of LADA. Velocity of flow in LADA was measured before and 2 min after cessation of intravenous infusion of dipyridamole (0.56 mg/kg in 4 min). The dipyridamole: rest mean diastolic velocity ratio was considered as an index of coronary flow reserve (CFR). For 20 of 21 patients with CFR > 2 there was no restenosis, whereas coronary angiography revealed restenosis in eight of nine patients with CFR < 2. The sensitivity was 88.9% and the specificity was 95.2%. For the 21 patients without restenosis mean CFR was 2.1 +/- 0.1 72 h after PTCA, had increased to 3.1 +/- 0.3 (P < 0.0001) 3 months after PTCA, and remained stable thereafter (3.0 +/- 0.9).

CONCLUSION

CFR after PTCA of proximal LADA can be evaluated serially by transesophageal Doppler echocardiography. CFR of LADA in patients without restenosis is increased 3 months after PTCA and remains stable thereafter.

Improvement of myocardial perfusion reserve early after coronary intervention: assessment with cardiac magnetic resonance imaging

OBJECTIVES

The purpose of this study was to determine the potential value of magnetic resonance myocardial perfusion in the follow-up of patients after coronary intervention.

BACKGROUND

In some patients a residual impairment of myocardial perfusion reserve (MPR) early after successful coronary intervention has been observed. In this study we evaluated an MPR index before and after intervention with magnetic resonance.

METHODS

Thirty-five patients with single- and multivessel coronary artery disease were studied before and 24 h after intervention. The signal intensity time curves of the first pass of a gadolinium-diethylene triamine pentacetic acid bolus injected via a central vein catheter were evaluated before and after dipyridamole infusion. The upslope was determined using a linear fit. Myocardial perfusion reserve index was estimated from the alterations of the upslope.

RESULTS

The MPR index in segments perfused by the stenotic artery was significantly lower than in the control segments (1.07 +/- 0.24 vs. 2.18 +/- 0.35, p < 0.001) and improved significantly after intervention (1.89 +/- 0.39, p < 0.001) but did not normalize completely (p < 0.01). After intervention the MPR index remained significantly lower in the balloon percutaneous transluminal coronary angioplasty group (1.72 +/- 0.38; n = 13) in comparison with the stent group (1.99 +/- 0.36, n = 18, p < 0.05). In the stent group a complete normalization of the MPR index was found 24 h after stenting.

CONCLUSIONS

Magnetic resonance perfusion measurements allow a reliable assessment of MPR index. An improvement of MPR index can be observed after coronary intervention, which is more pronounced after stenting. Magnetic resonance perfusion measurements allow the assessment and may be useful for the follow-up of patients with coronary artery disease after coronary intervention.

Limitation of coronary reserve after successful angioplasty is prevented by oral pretreatment with an alpha1-adrenergic antagonist

Coronary vasoconstriction that occurs after percutaneous transluminal coronary angioplasty (PTCA) is abolished by intracoronary phentolamine. An impairment of coronary vasodilator reserve (CVR) has been observed < or = 7 days after successful PTCA. To ascertain whether pretreatment with the alpha1-adrenergic receptor blocker doxazosin could prevent the limitation of CVR after PTCA, we carried out a randomised, double-blind, controlled study on 26 patients with significant (> 75%) single vessel disease undergoing PTCA. Twelve patients received doxazosin 4 mg daily in addition to their standard treatment, while 14 patients received matching placebo, starting 11 days before PTCA. Myocardial blood flow (MBF) at baseline and after i.v. dipyridamole (0.56 mg/kg) was measured within 5 days after PTCA using positron emission tomography (PET) with oxygen-15-labelled water. Angioplasty was successful in all patients with a residual stenosis < or = 35%. At PET scanning, hemodynamic parameters were comparable in the two groups. In the territory subtended by the dilated artery, CVR was significantly higher in patients treated with doxazosin compared with those receiving placebo (2.78 +/- 0.1.21 vs. 1.95 +/- 0.68; p < 0.01). Conversely, CVR in the remote territories subtended by angiographically normal arteries was similar in the two groups (2.53 +/- 0.92 and 2.48 +/- 0.80, respectively; p = NS). Treatment with oral doxazosin in addition to standard antianginal therapy can prevent the impairment of CVR frequently observed despite successful PTCA.

Improved coronary artery flow after coronary angioplasty in patients with unstable angina

BACKGROUND

Coronary artery flow is impaired after myocardial infarction but there is limited information regarding coronary flow in unstable angina.

AIM

To assess baseline coronary artery flow and the effects of coronary angioplasty on coronary flow in patients with unstable angina.

METHODS

Twenty-one patients with unstable angina with a culprit lesion suitable for coronary angioplasty were enrolled in the study. Coronary flow was assessed with the Thrombolysis In Myocardial Infarction (TIMI) grade and the Corrected TIMI Frame Count (CTFC) pre and post angioplasty.

RESULTS

Baseline flow was impaired in the culprit artery compared to the non culprit artery (42.0+/-28.1 vs 25.3+/-7.0 frames, p<0.02). Pre angioplasty coronary flow was TIMI grade 2 in 52% and TIMI grade 3 in 48% of patients. Post angioplasty flow improved with TIMI grade 2 flow in 5% and TIMI grade 3 in 95%. After angioplasty coronary flow improved from 42.0+/-28.1 frames to 21.6+/-16.3 (p=0.0001). The culprit coronary stenosis decreased from 74+/-9% pre angioplasty to 28+/-12% after intervention (p=0.0001).

CONCLUSIONS

Angioplasty and stenting of the culprit vessel restores normal coronary flow in most patients with unstable angina. This suggests that impaired flow in unstable angina is predominantly related to the culprit lesion residual stenosis.

Coronary physiology revisited : practical insights from the cardiac catheterization laboratory

Various coronary physiological measurements can be made in the cardiac catheterization laboratory using sensor-tipped guidewires; they include the measurement of poststenotic absolute coronary flow reserve, the relative coronary flow reserve, and the pressure-derived fractional flow reserve of the myocardium. Ambiguity regarding abnormal microcirculation has been reduced or eliminated with measurements of relative coronary flow reserve and fractional flow reserve. The role of microvascular flow impairment can be separately determined with coronary flow velocity reserve measurements. In addition to lesion assessment before and after intervention, emerging applications of coronary physiology include the determination of physiological responses to new pharmacological agents, such as glycoprotein IIb/IIIa blockers, in patients with acute myocardial infarction. Measurements of coronary physiology in the catheterization laboratory provide objective data that complement angiography for clinical decision-making.

[Anti-ischemic effect of verapamil within the scope of interventional recanalization]

We report on a 46-year-old male with unstable angina pectoris due to a total proximal occlusion of the left circumflex artery. At the side of a plaque rupture there was a thrombotic occlusion. With PTCA recanalization was possible, but a dissection occurred, therefore coronary stents were implanted. Besides an optimal morphological result and recurrent applications of nitroglycerin, the baseline blood flow velocity declined from initial 16 cm/s to 11 cm/s after PTCA down to 8.4 cm/s after stent implantation. Because peak flow velocity remained almost unchanged, the low baseline velocity ("slow flow phenomenon") did not lead to an impaired coronary flow velocity reserve (CFVR). Only after application of 1 mg verapamil, a sustained flow velocity on a higher baseline level was reached (17 cm/s), at the same time typical signs of ischemia in the ECG (ST-segment depressions) improved. Additionally, in the non-treated LAD there was an increase in coronary blood flow velocity from 10 cm/s up to 25 cm/s. The reduction in coronary blood flow velocity with increasing manipulations might be due to an impairment of the coronary microcirculations with increasing alpha-adrenergic vasoconstriction, a distribution of vasoactive agents and peripheral microembolizations. Only after administration of verapamil, a calcium channel blocker with non-specific anti-adrenergic effects, the slow flow was removed and ECG signs of ischemia improved. The blood flow velocity in the non-treated LAD was low at baseline and improved after verapamil. This phenomenon leads to the conclusion that mechanisms with vasoconstrictive effect are present in the whole coronary system, but these mechanisms are less pronounced in non-treated vessels.

Prevalence of microvascular disease in patients with significant coronary artery disease

Coronary flow velocity reserve (CFVR) measurement using intracoronary Doppler techniques has been increasing accepted for the assessment of physiological significance of epicardial stenosis and the functional changes after coronary interventions. However, large discrepancy exists concerning the acute changes of CFVR immediately after intervention. The purpose of this study was to investigate the prevalence of microvascular dysfunction in patients with significant coronary artery disease. Intracoronary Doppler flow measurements were performed in a total of 212 patients who underwent coronary interventions because of significant epicardial stenosis using 0.014" Doppler flow wire (Cardiometrics, Inc, Mountain View, CA). Intracoronary bolus injection of adenosine (12 micrograms for the right coronary and 18 micrograms for the left coronary arteries) was used to induce hyperemic reaction. CFVR was registered as the ratio of average peak velocity during hyperemia (hAPV) to at baseline (bAPV). Successful coronary interventions either by percutaneous transluminal coronary balloon angioplasty (PTCA) or by stenting could significantly improve the CFVR. In 80 patients with PTCA, the bAPV elevated from 16.6 +/- 2.1 cm/s to 20.6 +/- 13.4 cm/s and hAPV from 30.1 +/- 15.9 cm/s to 45.2 +/- 17.7 cm/s (both p < 0.001) with PTCA and the CFVR increased from 1.94 +/- 0.78 to 2.58 +/- 0.87 correspondingly (p < 0.001). Significant elevation of coronary flow parameters were also found in 132 patients with subsequent stent implantation (bAPV from 15.3 +/- 6.7 cm/s to 18.7 +/- 9.1 cm/s, hAPV from 28.7 +/- 14.4 cm/s to 44.3 +/- 17.7 cm/s and CFVR from 1.90 +/- 0.70 to 2.59 +/- 0.87, all p < 0.001). Reduction of CFVR (< 3.0) after intervention still existed in 46 (61.3%) of 80 patients after PTCA and 88 (66.7%) of 132 patients after stenting. Moreover, CFVR < 3.0 were found in 50 (45.9%) of 109 reference vessels in patients with single vessel disease. Significant improvement of coronary flow velocity and coronary flow velocity reserve could be obtained after successful angioplasty. However, microvascualr dysfunction existed in a large proportion of patients either in normal reference vessels or in target vessels after interventions.

Effect of stenting on coronary flow velocity reserve: comparison of coil and tubular stents

OBJECTIVE

To determine whether coil stents are as effective as tubular stents in improving coronary flow velocity reserve (CFVR) after stent deployment.

METHODS

Distal CFVR was measured with a 0. 014 inch Doppler guide wire before and after stenting in 33 patients. A coil stent was implanted in 16 patients and a tubular stent was used in 17 patients. Coronary flow velocity within the stent was also recorded during a slow pullback.

RESULTS

Following placement of the stents, the percentage diameter stenosis was similar for both the tubular and coil stents (mean (SE) 11 (2)% v 13 (2)%, NS). However, distal CFVR was higher after stenting with a tubular stent compared with a coil stent (2.46 (0.13) v 1.96 (0.14), p < 0.05). Furthermore, pullback through the stent detected a major flow velocity increase within coil stents but not in tubular stents (83 (24)% v 5 (5)%, p < 0.05).

CONCLUSIONS

In spite of similar angiographic improvement, placement of coil stents was associated with inferior functional results compared with tubular stents. The flow velocity acceleration within the coil stents suggests the presence of a residual narrowing within the stent, which is not appreciated on angiography.

Early recovery of coronary flow reserve after stent implantation as assessed by positron emission tomography

OBJECTIVES

The aim of this study was to quantitatively evaluate myocardial flow reserve in patients early after coronary stent implantation using positron emission tomography.

BACKGROUND

Delayed restoration of coronary flow reserve after percutaneous transluminal coronary angioplasty (PTCA) has been observed using a variety of techniques. Altered distal vasoregulation as well as residual stenosis have been considered possible explanations for this phenomenon. Although the implantation of stents may influence some of these mechanisms, little data are available characterizing coronary flow reserve early after stent placement.

METHODS

In 14 patients 1.6 +/- 0.6 days after stenting, N-13-ammonia positron emission tomographic studies were performed at rest and during adenosine-induced vasodilation. Myocardial blood flow was quantified using a three-compartment model. Rest and stress flow data, as well as coronary flow reserve of stented vascular territories, were compared with that of remote areas.

RESULTS

The stenosis decreased from 72.1 +/- 7.3% to 3.7 +/- 6.7% after stent implantation. Coronary flow in the stented areas did not differ significantly from that in remote areas either at rest (76.1 +/- 18.5 and 75.7 +/- 17.7 ml/min/100 g, respectively), or during maximal vasodilation (205.5 +/- 59.9 and 179.4 +/- 47.4 ml/min/100 g, respectively). In addition, there was no significant difference in the calculated values of coronary reserve of these two regions (2.74 +/- 0.64 and 2.43 +/- 0.55, respectively).

CONCLUSIONS

The mechanical support of dilated arteries by a stent not only restores the macroscopic integrity of epicardial arteries, but also results, in contrast to conventional PTCA procedures, in early recovery of flow reserve.

Measuring maximal percent area stenosis poststent placement with intracoronary Doppler and the continuity equation and correlation with intracoronary ultrasound and angiography

Quantitative coronary angiography (QCA) and intracoronary ultrasound (ICUS) are methods for anatomic assessment of stent deployment. Intracoronary Doppler is primarily a method for the physiologic assessment of coronary stenoses. It correlates well with traditional noninvasive measurements of lesion significance. Intracoronary Doppler was used for the anatomic assessment of de novo coronary artery stenosis with variable success; however, its use for anatomic assessment of adequate stent deployment is unavailable. A rapid, automated software program was developed based on a modified continuity equation to calculate the maximal in-stent percent area stenosis by comparing the maximal in-stent velocity to an average reference velocity (proximal and distal). This study was designed to compare the Doppler method of an anatomic assessment with QCA and ICUS in 15 patients. Physiologic success of stent deployment was determined by the distal coronary flow reserve to 24 to 36 microg of intracoronary adenosine. Following successful stent deployment, distal coronary flow reserve increased significantly from a baseline of 1.6 +/- 0.5 to 2.9 +/- 1.1. There was a significant correlation between the maximal in-stent percent area stenosis as measured by Doppler and both QCA (r = 0.78, p <0.01) and ICUS (r = 0.84, p <0.01). This study demonstrates that maximal in-stent percent area stenosis can be measured by intracoronary Doppler and a novel software program. The intracoronary Doppler guidewire method can assess the adequacy of stent deployment using both anatomic and physiologic principles and may supplement other quantitative methodologies.

Early alteration of coronary hemodynamics in late restenosis after coronary angioplasty

It is not known whether changes in coronary hemodynamics may antedate the development of restenosis after percutaneous coronary transluminal angioplasty (PTCA). The purpose of this study was to evaluate the early change in coronary microvascular function in patients with late restenosis after PTCA. Coronary hemodynamics were studied in series before, immediately after, 2 weeks and 3 months after successful PTCA in 12 male patients with a single lesion of the left anterior descending coronary artery. In each patient, great cardiac venous flow (GCVF) and oxygen content were measured both at baseline and during hyperemia induced by adenosine infusion. The sequential changes of coronary hemodynamics were compared between patients with and without restenosis at 3 months after PTCA. Basic characteristics did not differ between the patients with (n = 6) and those without restenosis (n = 6). Luminal diameter stenosis (in percentage) was also similar between the two groups both before (79.2 +/- 18.4% vs 83.0 +/- 9.6%, p = NS) and up to 2 weeks after PTCA (25.8 +/- 10.9% vs 28.5 +/- 7.9%, p = NS). In patients without restenosis, basal and hyperemic GCVF was unchanged up to 2 weeks after PTCA. There was a significant increase in CFR 3 months after PTCA. In patients with restenosis, basal GCVF was significantly increased and hyperemic GCVF was unchanged immediately after PTCA. However, 2 weeks after PTCA, basal GCVF was decreased while luminal diameter was still preserved. In comparison with those without restenosis, patients with restenosis had significantly lower CFR before (1.98 +/- 0.42 vs 2.69 +/- 0.46, p = 0.019), immediately after (1.47 +/- 0.27 vs 2.24 +/- 0.47, p = 0.006) and 3 months after PTCA (1.51 +/- 0.32 vs 3.40 +/- 0.54, p = 0.001). In patients without restenosis, the recovery of coronary microvascular function was delayed up to 3 months after PTCA. In patients with late restenosis, basal coronary microvascular tone was altered within 2 weeks after PTCA suggesting early deterioration of coronary microvascular function before the development of angiographic restenosis.

Alpha-adrenergic blockade improves recovery of myocardial perfusion and function after coronary stenting in patients with acute myocardial infarction

BACKGROUND

AMI reperfusion by thrombolysis does not improve TIMI flow and LV function. The role of infarct-related artery (IRA) stenosis and superimposed changes in coronary vasomotor tone in maintaining LV dysfunction must be elucidated.

METHODS AND RESULTS

Forty patients underwent diagnostic angiography 24 hours after thrombolysis. Seventy-two hours after thrombolysis, the culprit lesion was dilated with coronary stenting. During angioplasty, LV function was monitored by transesophageal echocardiography. Percent regional systolic thickening was quantitatively assessed before PTCA, soon after stenting, 15 minutes after stenting, and after phentolamine 12 microg/kg IC (n=10), the alpha1-blocker urapidil 600 microg/kg IV (n=10), or saline (n=10). Ten patients pretreated with beta-blockers received urapidil 10 mg IC. Coronary stenting significantly improved thickening in IRA-dependent and in non-IRA-dependent myocardium (from 27+/-15% to 38+/-16% and from 40+/-15% to 45+/-15%, respectively). Simultaneously, TIMI frame count decreased from 39+/-11 and 40+/-11 in the IRA and non-IRA, respectively, to 23+/-10 and 25+/-7 (P<0.05). Fifteen minutes after stenting, thickening worsened in both IRA- and non-IRA-dependent myocardium (to 19+/-14% and 28+/-14%, P<0.05), and TIMI frame count returned, in both the IRA and non-IRA, to the values obtained before stenting. Phentolamine and urapidil increased thickening to 36+/-17% and 41+/-14% in IRA and to 48+/-11% and 49+/-17% in non-IRA myocardium respectively, and TIMI frame count decreased to 16+/-6 and to 17+/-5, respectively. Changes were attenuated with beta-blocker pretreatment.

CONCLUSIONS

Our finding that alpha-adrenergic blockade attenuates vasoconstriction and postischemic LV dysfunction supports the hypothesis of an important role of neural mechanisms in this phenomenon.

Immediate and long-term effect of balloon angioplasty or stent implantation on the absolute and relative coronary blood flow velocity reserve

BACKGROUND

There is controversy regarding the immediate and long-term effects of PTCA on the coronary flow reserve.

METHODS AND RESULTS

A total of 54 patients with 1-vessel disease and normal left ventricular function were studied after balloon angioplasty (n=34) or stent implantation (n=20). Distal coronary blood flow velocity reserve (CFR) was defined as the ratio of adenosine-induced hyperemic versus baseline blood flow velocity with a 0.014-in Doppler guidewire. The relative CFR was defined as the ratio of the distal CFR and the reference CFR measured in the normal adjacent coronary artery. Hemodynamic and angiographic measurements were performed before and directly after balloon angioplasty or stent implantation and at 6-month follow-up. CFR after PTCA </=2.5 was defined as an impaired CFR. Immediately after PTCA, CFR improved toward the range of the reference artery CFR. In both the balloon-treated and the stent-treated groups, initial high CFR values decreased and impaired CFR values increased at follow-up toward the values of the reference CFR in patients without restenosis. Impaired CFR after balloon angioplasty (33%) or stent implantation (58%) in patients without restenosis was related to an increased baseline flow velocity that normalized at follow-up. Patients with an increase of CFR after stenting were characterized by an unaltered baseline flow velocity and an increased adenosine-induced hyperemic flow velocity.

CONCLUSIONS

An impaired CFR (</=2.5) is a frequent finding after balloon angioplasty or stent implantation as a result of a high baseline flow velocity. Normalization of impaired CFR at follow-up in patients without restenosis was associated with a decline of the baseline flow velocity after both balloon angioplasty and stent implantation, supporting the contention that this phenomenon relates to a slow recovery of autoregulation of the microvascular bed.

Does coronary stenting following balloon angioplasty improve myocardial fractional flow reserve?

PURPOSE

Suboptimal distal coronary flow reserve after successful balloon angioplasty has been attributed to angiographically unrecognized inadequate lumen expansion, and adjunct coronary stenting has been shown to improve coronary flow reserve. The aim of this study was to investigate whether myocardial fractional flow reserve (FFRmyo) would increase further after coronary stenting compared with balloon angioplasty alone in the same patient group.

METHODS

FFRmyo and quantitative coronary angiography were obtained before and after pre-stent balloon dilation, and again after stent placement in 11 patients (7 left anterior descending artery, 3 right coronary artery and 1 left circumflex artery). FFRmyo was calculated as the ratio of Pd/Pa during intracoronary adenosine 5'-triphosphate (50 micrograms and 20 micrograms in the left and right coronary arteries, respectively)-induced maximum hyperemia, where Pd represents mean distal coronary pressure measured by a 2.1 Fr infusion catheter and Pa represents mean aortic pressure measured by the guiding catheter.

RESULTS

Percent diameter stenosis significantly decreased after balloon angioplasty (74% +/- 15% vs 37% +/- 17%, p < 0.001), and decreased further after stent placement (18% +/- 10%, p < 0.001 vs baseline and balloon angioplasty). FFRmyo after coronary stenting (0.85 +/- 0.09) was significantly higher than that at baseline (0.51 +/- 0.16, p < 0.001) and after balloon angioplasty (0.77 +/- 0.11, p < 0.05). There was a significant correlation between angiographic variables and FFRmyo. The increase in lumen dimensions after coronary stenting was followed by a further significant improvement of FFRmyo.

CONCLUSION

These results suggest that coronary stenting may provide a more favorable functional status and lumen geometry of residual coronary stenosis compared with balloon angioplasty alone.

Comparison of coronary flow velocity and regional myocardial perfusion for functional evaluation of coronary artery disease in the setting of angioplasty

Two essentially different methods for physiological evaluation of coronary artery disease were compared in the setting of angioplasty and related to quantitative coronary angiography. Forty-five patients, referred for percutaneous transluminal coronary angioplasty (PTCA), were examined by digital subtraction angiography (DSA) and by coronary flow velocity measurements distal to the target stenosis. Before PTCA, hyperemic mean transit time (HMTT) was correlated with % area stenosis r = 0.56*, coronary flow velocity reserve (CFVR) r = 0.58* and with CFVRN (CFVR normalized to a mean blood pressure of 100 mmHg) r = 0.68*. The correlation between CFVR and % area stenosis was r = 0.72* (*P < 0.001). After PTCA, all correlations between these measurements disappeared. HMTT and CFVR remained abnormal in 18% and 32 % of the patients, respectively. Pre-PTCA, distal coronary flow velocity measurements were reasonably well related to the assessment of regional myocardial perfusion. Flow velocity parameters, however, were better related to angiographic stenosis parameters. After PTCA, HMTT showed a more consistent improvement compared to CFVR. Flow velocity measurements appear to be more useful for the evaluation of local coronary stenoses, whereas the assessment of regional myocardial perfusion by DSA may be used for a more general evaluation of vessel territories.

Current concepts of coronary flow reserve for clinical decision making during cardiac catheterization

Measurements of coronary flow reserve, once used only for research, have gained wide acceptance as an additional diagnostic approach in the decision-making process of diagnostic cardiac catheterization and coronary interventions. Apart from the noninvasive determination of coronary flow reserve, intracoronary Doppler flow wires have facilitated decision making in the catheterization laboratory. Different techniques, unstandardized procedures, and data from uncomparable patient populations have remained a confounding factor. This review examines current concepts of coronary flow reserve as well as methodologic considerations and pitfalls. Applications of coronary flow reserve for periinterventional assessment are evaluated on the background of practical guidance. According to a detailed examination of arterial structure and function, a normal coronary flow reserve exceeds a value of 3.0. Values below 3.0 suggest involvement of microvascular disease caused by functional or structural alterations. The influences of various factors such as age, hemodynamics, hypercholesterolemia, hypertrophy, hypertension, syndrome X, and coronary artery disease are discussed in relation to the effect on coronary flow reserve. From available information, measurements of coronary flow reserve are an adjunct to current interventional technology to optimize individual patient care. Further efforts should be undertaken to incorporate these new methods into our routine clinical decision making.

Use of the continuity equation for transesophageal Doppler assessment of severity of proximal left coronary artery stenosis: a quantitative coronary angiography validation study

OBJECTIVES

We tested the value of transesophageal Doppler echocardiography (TEDE) for quantitating proximal left coronary artery (LCA) stenosis by using the continuity equation.

BACKGROUND

The continuity equation applied to a stenosis states that the ratio of the time-velocity integral (TVI) of prestenotic to stenotic flow velocities is equal to the ratio of stenotic to prestenotic cross-sectional areas. TEDE allows the measurement of coronary blood flow velocities within the proximal part of the LCA. METHODS; Forty-one patients with a stenosis of the proximal or mid left anterior descending coronary artery or with a nonostial stenosis of the left main coronary artery were studied. Coronary flow velocities were recorded by TEDE guided by color flow imaging. Prestenotic velocities were recorded by pulsed Doppler echocardiography and transstenotic velocities were recorded by pulsed or high pulse repetition frequency or continuous wave Doppler echocardiography. The prestenotic and transstenotic diastolic TVIs were calculated and the TEDE-derived percent area stenosis was calculated as (1 - TVI ratio) x 100. Quantitative angiography lesion analysis was performed using a computer-assisted automated edge-detection system.

RESULTS

TEDE recordings were successful in 35 of the 41 patients. A good linear correlation was found between TEDE and quantitative angiographically derived percent area stenosis (r = 0.89, p = 0.0001, SEE 5.7). However, TEDE measurements underestimated the actual percent area stenosis (slope of regression 0.54). A better agreement (slope 1.08) was obtained after dividing prestenotic velocity by 2 in the continuity equation, based on the assumption of a parabolic cross-sectional velocity profile in the prestenotic segment.

CONCLUSIONS

TEDE may be used for quantitating stenosis of the proximal part of the LCA with the use of a modified continuity equation that takes into account the parabolic velocity profile in the normal prestenotic segment.

Quantitative angiography of coronary artery dimensions 24 hours after rotational atherectomy

Rotational atherectomy results in platelet activation and heat generation, which may impact artery size immediately after treatment. In addition, arteries treated with balloon angioplasty may exhibit recoil within 24 hours. In this study, arteries treated with rotational atherectomy, with and without adjunctive balloon angioplasty, were analyzed by quantitative coronary angiography to determine the effect of rotational atherectomy on the dynamic behavior of the arterial wall within 24 hours after the procedure. Quantitative coronary angiography was performed at a core laboratory. Coronary angiogram acquisitions were preceded by intracoronary nitroglycerin injections and were repeated using identical angles of projection. Proximal and distal reference vessel diameters were 2.55 +/- 0.60 and 2.28 +/- 0.51 mm, respectively, and did not change from pre- to postprocedure. Both were larger the following day increasing to 2.72 +/- 0.65 and 2.52 +/- 0.52 mm, respectively, (p <0.001). Minimum luminal diameter (MLD) increased from 0.70 +/- 0.28 mm before to 1.49 +/- 0.34 mm after the procedure and to 1.72 +/- 0.37 mm at 24-hour follow-up (p <0.001). Subset analysis of patients treated with rotational atherectomy alone or rotational atherectomy with adjunctive balloon angioplasty revealed that the increase in luminal diameters occurred in both subsets. Patients treated with adjunctive angioplasty had a smaller initial MLD, a larger postprocedure MLD, and no difference in MLD at 24-hour follow-up compared with stand-alone rotational atherectomy. Subset analysis of 100 patients who had 6-month follow-up angiography revealed that both a calculated acute gain and chronic late loss, based on a 24-hour film, differed significantly from values using a film acquired immediately after the procedure. However, the slope of the linear regression between acute gain and chronic late loss did not differ. Coronary arteries treated with rotational atherectomy with or without adjunctive balloon angioplasty increase significantly in size during the first 24 hours after the procedure. This phenomenon has implications for the calculation of absolute gain and chronic late loss, but not for the linear relation between the 2 quantitative outcomes.

Postischemic left ventricular dysfunction is abolished by alpha-adrenergic blocking agents

OBJECTIVES

We sought to evaluate the efficacy of alpha-adrenergic blocking agents in counteracting left ventricular (LV) dysfunction occurring after transient ischemia in humans.

BACKGROUND

The mechanisms underlying postischemic LV dysfunction are largely unknown.

METHODS

Percutaneous transluminal coronary angioplasty (PTCA) provides a clinical model of ischemia and reperfusion. In 50 patients undergoing coronary stenting for 77+/-5% stenosis, LV function was monitored by transesophageal echocardiography during and 30-min after PTCA. Fifteen minutes after stenting, 15 patients received 12 microg/kg body weight of the alpha-blocker phentolamine intracoronarily, 15 patients received 600 microg/kg of the alpha1-blocker urapidil intravenously, 10 patients received the combination of phentolamine and 1.2 mg of propranolol intracoronarily, and 10 patients received saline.

RESULTS

Fifteen minutes after successful coronary dilation, significant contractile dysfunction occurred in previously ischemic and nonischemic myocardium. LV dysfunction was accompanied by an increase in coronary resistance and diffuse vasoconstriction. Alpha-blockers counteracted LV dysfunction and coronary resistance and the increase in vasoconstriction. Phentolamine and urapidil increased global LV shortening from 34+/-9% to 45+/-8% and to 49+/-8%, respectively (p < 0.05). After the administration of propranolol combined with phentolamine, LV dysfunction remained unchanged (34+/-6%), as in control subjects.

CONCLUSIONS

LV dysfunction occurs after PTCA, as described in animal models after ischemia. Alpha-blockers abolished LV, macrocirculatory and microcirculatory dysfunction, whereas the alpha-blocker effect was prevented by combining alpha- and beta-blockers. The evidence of diffuse rather than regional dysfunction, together with the opposite effects of alpha- and beta-blockade, supports the hypothesis of neural mechanisms eliciting postischemic LV dysfunction.

Comparison of intracoronary Doppler guide wire and transesophageal echocardiography in measurement of flow velocity and coronary flow reserve in the left anterior descending coronary artery

BACKGROUND

The intracoronary Doppler tipped guide wire has been shown to be highly accurate in the measurement of coronary flow velocity (CFV). Recent studies have indicated that blood flow velocity in the left anterior descending coronary artery (LAD) can be determined by transesophageal echocardiography (TEE). The purpose of this study was to compare flow velocity recordings and coronary flow reserve measurements in the LAD by TEE with those obtained by Doppler guide wire.

METHODS AND RESULTS

The study population consisted of 14 patients with chest pain and normal coronary arteriograms. After routine coronary arteriography was performed, a 0.014-inch Doppler guide wire was advanced into the proximal part of the LAD. After baseline measurement of coronary flow velocity (CFV) was obtained, 140 microg/kg/min adenosine was administered intravenously for 3 minutes, and the flow velocity was recorded. TEE was performed within 24 hours of the cardiac catheterization. After baseline measurements of CFV in the LAD, heart rate, and blood pressure were obtained, 140 microg/kg/min adenosine was administered intravenously, and the CFV was recorded. Coronary flow reserve was calculated as the ratio of the peak diastolic CFV during adenosine infusion to the peak diastolic CFV at baseline. A good correlation was found (r = 0.91, p < 0.0001) between CFV by Doppler guide wire and that determined by TEE. A good correlation was also found between the coronary flow reserve assessed by Doppler guide wire and that determined by TEE (r = 0.92, p < 0.0001).

CONCLUSION

Our data indicate that CFV and coronary flow reserve in the LAD can be accurately measured by transesophageal echocardiography.

Noninvasive analysis of coronary artery poststenotic flow characteristics by using transthoracic echocardiography

This study was performed (1) to test whether transthoracic echocardiography may detect coronary flow velocity in the left anterior descending coronary artery distal to stenoses; and (2) to noninvasively assess coronary artery hemodynamics distal to coronary artery stenoses. High-frequency transthoracic echocardiography was used to assess blood velocity patterns in the distal segment of the left anterior descending coronary artery of 128 consecutive patients (mean age, 58 +/- 9 years; 97 men and 31 women) who underwent cardiac catheterization for investigation of angina. Biphasic, diastolic predominant Doppler velocity patterns were obtained in 67 patients (52%). There was no significant difference in any measurements of systolic blood velocity between patients with unobstructed (less than 30% stenosis) left anterior descending coronary artery, moderate stenosis (30% to 70% obstruction), or severe stenosis (more than 70% obstruction). Patients with severe stenosis demonstrated a reduction in the diastolic component of blood flow velocity in the distal left anterior descending coronary artery compared with patients in the other two groups. This technique may be useful for the noninvasive assessment of the significance of stenotic left anterior descending coronary artery disease or the outcome of interventional procedures.

Prognostic value of intracoronary flow velocity and diameter stenosis in assessing the short- and long-term outcomes of coronary balloon angioplasty: the DEBATE Study (Doppler Endpoints Balloon Angioplasty Trial Europe)

BACKGROUND

The aim of this prospective, multicenter study was the identification of Doppler flow velocity measurements predictive of clinical outcome of patients undergoing single-vessel balloon angioplasty with no previous Q-wave myocardial infarction.

METHODS AND RESULTS

In 297 patients, a Doppler guidewire was used to measure basal and maximal hyperemic flow velocities proximal and distal to the stenosis before and after angioplasty. In 225 patients with an angiographically successful percutaneous transluminal coronary angioplasty (PTCA), postprocedural distal coronary flow reserve (CFR) and percent diameter stenosis (DS%) were correlated with symptoms and/or ischemia at 1 and 6 months, with the need for target lesion revascularization, and with angiographic restenosis (defined as DS > or = 50% at follow-up). Logistic regression and receiver operator characteristic curve analyses were applied to determine the prognostic cutoff value of CFR and DS separately and in combination. Optimal cutoff criteria for predictors of these clinical events were DS, 35%; CFR, 2.5. A distal CFR after angioplasty > 2.5 with a residual DS < or = 35% identified lesions with a low incidence of recurrence of symptoms at 1 month (10% versus 19%, P=.149) and at 6 months (23% versus 47%, P=.005), a low need for reintervention (16% versus 34%, P=.024), and a low restenosis rate (16% versus 41%, P=.002) compared with patients who did not meet these criteria.

CONCLUSIONS

Measurements of distal CFR after PTCA, in combination with DS%, have a predictive value, albeit modest for the short- and long-term outcomes after PTCA, and thus may be used to identify patients who will or will not benefit from additional therapy such as stent implantation.

Measurement of myocardial fractional flow reserve during coronary angioplasty in patients with old myocardial infarction

Although myocardial fractional flow reserve (FFRmyo) has been demonstrated to be a useful index for determining functional significance of coronary stenosis, the data in previous studies was derived from a highly selected group of patients. The aim of this study was to investigate the value of FFRmyo in a more clinically relevant group of patients, especially in patients who also had resistance vessel dysfunction. We measured FFRmyo in 20 consecutive patients who had undergone elective coronary angioplasty. FFRmyo was calculated by the ratio of Pc/Pa during intracoronary adenosine 5'-triphosphate (ATP; 50 micrograms in the left coronary and 20 micrograms in the right coronary artery) induced maximal hyperemia, where Pa represents mean aortic pressure obtained by the guiding catheter and Pc represents mean distal coronary pressure measured by a 2.1 F infusion catheter. In total, 21 vessels were dilated and 14 of them were infarct-related arteries. The percent diameter stenosis significantly decreased from 80 +/- 14% to 27 +/- 17%, and the FFRmyo increased significantly from 0.46 +/- 0.18 to 0.77 +/- 0.15 after angioplasty. There was no significant differences in the FFRmyo between vessels with previous myocardial infarction and those without, after angioplasty (0.78 +/- 0.18 vs. 0.76 +/- 0.08). There was a significant correlation between the percent diameter stenosis and FFRmyo before (r = 0.83, P < 0.001) and after (r = 0.64, P < 0.01) angioplasty. In conclusion, FFRmyo significantly improved immediately after angioplasty in vessels with myocardial infarction as well as those without. These results led us to suggest the usefulness of FFRmyo in patients who had both epicardial stenosis and resistance vessel dysfunction. The significant correlation between FFRmyo and quantitative coronary arterial diameter stenosis would further support the more widespread use of FFRmyo in the clinical setting.

Evaluation of successful PTCA by transstenotic flow velocity ratios

Doppler probes mounted on the tip of a guidewire allow the measurement of coronary blood flow velocities, not only proximal but also distal to stenoses eligible for percutaneous transluminal coronary angioplasty (PTCA). The objective of this study was to determine the improvement of transstenotic Doppler flow velocity ratios following PTCA and to investigate the possible impact on restenosis during follow-up control angiography three months later. Doppler flow velocity measurements were performed in 29 patients with 29 stenoses eligible for PTCA. Results of PTCA were morphologically evaluated by computer-assisted quantitative coronary angiography (QCA) and measured hemodynamically by determining transstenotic Doppler flow velocity ratios. Successful PTCA according to QCA was present in all cases with a reduction of mean diameter stenosis from 66 +/- 8% to 35 +/- 7%. Resting spectral peak velocities and velocity integrals were markedly reduced distal to lesions (all P < 0.001), resulting in mean transstenotic flow velocity and velocity integral ratios of less than 0.60 prior to PTCA. Owing to endoluminal enlargement, significant improvement of transstenotic Doppler ratios was observed in mean ratios greater than 0.90 (all P < 0.0001). In patients with restenosis, transstenotic ratios following PTCA demonstrated a tendency to be smaller than in patients without restenosis. Transstenotic Doppler flow velocity ratios are diminished in severe coronary stenoses. Improvement of these ratios provides information on hemodynamic success of interventional procedures. Thus, the determination of intracoronary Doppler flow velocity ratios contributes, in addition to angiographic estimation, to the evaluation of stenoses severity and success of interventional procedures.

From research to clinical practice: current role of intracoronary physiologically based decision making in the cardiac catheterization laboratory

Decisions regarding coronary interventions should be combined with objective evidence of myocardial ischemia. The most common physiologic approach utilizes hospital facilities outside the catheterization laboratory, requiring additional time and cost. With the introduction of sensor-tipped angioplasty guide wires, distal coronary flow velocity and pressure can be obtained in the cardiac catheterization laboratory, facilitating physiologically based decisions regarding the need for intervention. In the catheterization laboratory, physiologically significant stenoses can be characterized as having impaired post-stenotic coronary flow reserve < 2.0 and pressure-derived fractional flow reserve < 0.75, both variables related strongly to positive ischemic perfusion imaging or stress testing results. Deferring coronary interventions on the basis of normal translesional physiology is safe and is associated with a low rate (< 10%) of lesion progression over a 10-month follow-up period. Preliminary data indicate that excellent physiologic and anatomic end points after balloon angioplasty are associated with low (< 20%) restenosis rates at 6-month follow-up. Clinically relevant relations of in-laboratory physiology support the insight that physiologic, as much as or more than anatomic variables, ultimately determine the functional status of a patient. Current data suggest that an intracoronary physiologic approach complements coronary lumenology and appears to have important clinical and economic implications for patients undergoing invasive evaluation and treatment of coronary artery disease.

Role of coronary artery lumen enlargement in improving coronary blood flow after balloon angioplasty and stenting: a combined intravascular ultrasound Doppler flow and imaging study

OBJECTIVES

This study sought to examine the mechanism of increasing coronary flow reserve after balloon angioplasty and stenting.

BACKGROUND

Coronary vasodilatory reserve (CVR) does not improve after percutaneous transluminal coronary angioplasty in > or = 50% of patients, postulated to be due to impaired microvascular circulation or inadequate lumen expansion despite adequate angiographic results.

METHODS

To demonstrate the role of coronary lumen expansion, serial coronary flow velocity (0.014-in. Doppler guide wire) was measured in 42 patients before and after balloon angioplasty and again after stent placement. A subset (n = 17) also underwent intravascular ultrasound (IVUS) imaging of the target sites after angioplasty and stenting. CVR (velocity) was computed as the ratio of adenosine-induced maximal hyperemic to basal average peak velocity.

RESULTS

The percent diameter stenosis decreased from (mean +/- SD) 84 +/- 13% to 37 +/- 18% after angioplasty and to 8 +/- 8% after stenting (both p < 0.05). CVR was minimally changed from 1.70 +/- 0.79 at baseline to 1.89 +/- 0.56 (p = NS) after angioplasty but increased to 2.49 +/- 0.68 after stent placement (p < 0.01 vs. before and after angioplasty). IVUS lumen cross-sectional area was significantly larger after stenting than after angioplasty (8.39 +/- 2.09 vs. 5.10 +/- 2.03 mm2, p < 0.05). Anatomic variables were related to increasing coronary flow velocity reserve (CVR vs. IVUS lumen area: r = 0.47, p < 0.005; CVR vs. quantitative coronary angiographic percent area stenosis: r = 0.58, p < 0.0001).

CONCLUSIONS

In most cases, increases in CVR were associated with increases in coronary lumen cross-sectional area. These data suggest that impaired CVR after angioplasty is often related to the degree of residual narrowing, which at times may not be appreciated by angiography. A physiologically complemented approach to balloon angioplasty may improve procedural outcome.

Coronary blood flow velocities during rotational atherectomy

This study was designed to evaluate the alterations in doppler derived coronary blood flow velocities and flow reserve following rotational ablation. Changes in doppler derived coronary blood flow velocity variables have been valuable in assessing the physiological outcome following coronary balloon angioplasty. Rotational ablation's mechanism of plaque removal could alter distal vascular bed characteristics, and, as a result, intracoronary blood flow velocities and the coronary flow reserve. A 12-MHz doppler guidewire recorded intracoronary phasic velocities and coronary flow reserve (as assessed by the hyperemic response to adenosine [12-18 mcg intracoronary]) in 28 patients, before and after rotational ablation of 30 lesions. Adjunctive balloon angioplasty was performed in 27 of 28 patients (96%). Rotational ablation and adjunctive balloon angioplasty successfully reduced the lesion diameter (87 +/- 9% to 14 +/- 11%; P < 0.001). A significant increase in the mean distal average peak velocity (25 +/- 13 cm/sec, before; 47 +/- 22 cm/sec, after; P < 0.001), and decrease in the proximal to distal average peak velocity ratio, (2.1 +/- 1.3; to 1.2 +/- 0.4; P = 0.002) was recorded. The mean distal diastolic to systolic velocity ratio (before, 1.4 +/- 0.7; after, 1.6 +/- 0.8; P = 0.44) and the coronary flow reserve (before, 1.6 +/- 0.6; after, 1.5 +/- 0.5; P = 0.34) did not increase despite increases in distal velocities, following successful intervention. Doppler derived distal coronary blood flow velocities increased following rotational ablation and adjunctive balloon angioplasty, with resolution of transstenotic velocity gradient. Changes in distal phasic velocity pattern and coronary flow reserve, immediately after the intervention, were not useful in the assessment of the functional outcome and may be related to abnormalities in distal vascular bed vasoreactivity produced by rotational ablation.

Clinical application of coronary flow reserve using an intracoronary Doppler guide wire

Coronary flow reserve (CFR) is a critical measurement in the assessment of the coronary circulation. The development of this physiologic variable in animal and human studies is reviewed. Human studies documenting the limitations of coronary angiography, especially in the setting of severe diffuse coronary artery disease, are analyzed. Furthermore, the important variables that must be accounted for when CFR is measured are examined. With this background, the application of CFR in a variety of clinical settings and the development and use of the Doppler FloWire for its measurement are discussed.

Coronary vein flow velocity changes during transluminal balloon angioplasty: a study using the Doppler guide wire

The coronary flow velocity changes in the great cardiac and middle cardiac veins, induced by intracoronary administration of nitroglycerine, adenosine, and during percutaneous transluminal coronary angioplasty, were evaluated in 12 patients with significant coronary stenoses, using the Doppler wire (Flowire). Optimal spectral signals of the time-averaged peak flow velocity were obtained in 10 patients. Nitroglycerine produced no significant flow velocity changes (P = 0.13). Adenosine caused a significant augmentation of flow velocity compared to baseline (P = 0.003). During balloon inflation, venous flow velocity decreased (P = 0.007); however, the venous outflow did not cease. A pronounced venous hyperemic response, following balloon deflation, was also documented. The utility of continuous vein flow velocity monitoring with the Flowire, during high-risk and complicated coronary interventions remains to be elucidated.

Cardioesophageal reflex: a mechanism for "linked angina" in patients with angiographically proven coronary artery disease

OBJECTIVES

The purpose of this study was to investigate the presence of a cardioesophageal reflex in patients with coronary artery disease that may explain the mechanism of "linked angina."

BACKGROUND

It has been previously shown that esophageal acid stimulation can reduce coronary blood flow in patients with syndrome X, suggesting the presence of a cardioesophageal reflex in humans.

METHODS

We studied the effect of esophageal acid stimulation on coronary blood flow in 14 patients with angiographically documented significant coronary artery disease and in 18 heart transplant recipients. Hydrochloric acid (0.1 mol/liter) and 0.9% saline solution were infused in random, double-blind manner (60 ml over 5 min) through a fine-bore tube positioned in the patient's distal esophagus, and coronary blood flow measurements were obtained after each infusion by use of a 3.6F intracoronary Doppler catheter positioned in the proximal left anterior descending coronary artery.

RESULTS

Coronary blood flow was reduced significantly by esophageal acid stimulation in the coronary artery disease group (before acid 70.4 +/- 14.3 ml/min, after acid stimulation 46.4 +/- 19.1 ml/min [mean +/- SD], p < 0.01). However, there was no significant difference in coronary blood flow during saline infusion (73.5 +/- 15.3 vs. 72.5 +/- 14 ml/min). Coronary blood flow in the heart transplant group was not affected by acid or saline infusion.

CONCLUSIONS

Esophageal acid stimulation can cause animal attacks and significantly reduce coronary blood flow in patients with coronary artery disease. The lack of any significant effect in heart transplant recipients with heart denervation suggests a neural reflex.

Utilization of translesional hemodynamics: comparison of pressure and flow methods in stenosis assessment in patients with coronary artery disease

Aim of this study is the assessment of feasibility and clinical usefulness of a new index of stenosis severity, the slope of the instantaneous transstenotic pressure gradient/velocity relationship. Twenty-one patients scheduled for percutaneous revascularization procedures were studied with simultaneous measurement of poststenotic coronary pressure and flow velocity, in basal condition and during maximal hyperemia induced with intracoronary papaverine. Reliable measurements of the transstenotic pressure gradient/velocity relationship could be obtained in 11 patients. In 64% of the cases, a quadratic equation showed the best fit for the data. Steeper increases of the transstenotic pressure gradient at any given velocity increase were observed in the lesions with the smallest cross-sectional area measured with quantitative angiography. A comparison of this new index with coronary flow reserved, maximal hyperemic velocity, stenosis flow reserve derived from quantitative angiography, basal and hyperemic transstenotic pressure gradient and fractional flow reserve is presented and the relative merits of all these parameters are discussed. This pilot experience suggests that the instantaneous relationship between pressure gradient and flow velocity changes during the cardiac cycle can accurately characterize the stenosis hemodynamics in the catheterization laboratory.