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

Assessing the physiologic significance of coronary artery disease: role of Doppler methodology

It is important to define both anatomic and functional significance of coronary artery stenoses. Quantitative angiography has decreased the inter- and intraobserver variability in interpreting the coronary angiogram, but it is less clinically applicable in assessing functional significance. The coronary Doppler catheter and guidewire can provide considerable information regarding the functional effects and pathophysiology of coronary stenosis in humans at the time of cardiac catheterization. Clinically, it is a simple and safe technique which makes it feasible in a clinical setting to use it as a tool to assess the physiologic significance of an intermediate stenosis or the functional result of an interventional procedure. Other uses for the intravascular Doppler method, such as the evaluation of cardiac transplant vasculopathy and rejection and evaluation of patients with chest pain syndromes and normal coronary angiograms, are being studied. However, the usefulness of this technique in decision-making has yet to be fully clarified. Future clinical studies should be directed toward comparing this method with noninvasive methods, that is, exercise treadmill test and thallium studies, and attempt to answer questions regarding its prognostic value.

New concepts for interpretation of intracoronary velocity and pressure tracings

The development of quantitative angiography and the introduction of new imaging techniques cannot replace functional methods of assessing the severity of stenosis. Measurement of transstenotic pressure gradient and poststenotic flow velocity using miniaturised sensors with guidewire technology offers an alternative to the conventional non-invasive methods that is immediately applicable in the catheterisation laboratory during interventional procedures. The complexity of the coronary circulation, however, makes it difficult to establish simple cut-off criteria to identify the presence of a flow-limiting stenosis. For intermediate lesions or in the presence of variable haemodynamic conditions, the accuracy of the assessment can be improved by the application of more complex indices proposed and validated in the laboratory animals. Two of these indices are myocardial fractional flow reserve and the slope of the instantaneous relation between pressure or pressure gradient and flow velocity.

Maximal myocardial perfusion by videodensitometry in the assessment of the early and late results of coronary angioplasty: relationship with coronary artery measurements and left ventricular function at rest

In the assessment of the acute results of percutaneous transluminal coronary angioplasty (PTCA), myocardial perfusion at maximal vasodilatation theoretically has fewer limitations than the coronary flow reserve measurements and quantitative coronary angiography. The purpose of this study was to compare the myocardial perfusion to the measurements of the severity of the lesion (minimal luminal diameter and percent area stenosis) and to relate it to the changes of left ventricular function after PTCA. Regional myocardial perfusion was assessed during intracoronary papaverine, using the inverse mean transit time of contrast medium (1/Tmn), before, 15 min after, 18-24 hr after, and 6 months after successful single-vessel PTCA in 14 patients with stable angina. Left ventricular angiography (before angioplasty, 18-24 hr after, and 6 months later) was analysed by area-length and centerline methods. Immediately after PTCA, 1/Tmn increased from 0.14 +/- 0.07 sec-1 to 0.21 +/- 0.09 sec-1 (P = .001). Maximal myocardial perfusion remained higher than the pre-PTCA value the day after angioplasty (1/Tmn of 0.23 +/- 0.09 sec-1), while it reduced to near pre-PTCA values at follow-up (1/Tmn of 0.16 +/- 0.05 sec-1). Before PTCA, three out of ten patients had ejection fraction of < 65%, and seven had mild-to-moderate hypokinesis. The day after PTCA the ejection fraction and the regional dysfunction improved significantly. The change in ejection fraction 18-24 hr after PTCA did not correlate with minimal luminal diameter and percent area stenosis and correlated slightly with the improvement of perfusion (r = 0.54, P = .10). At follow-up left ventricular function deteriorated in the whole group, despite the persistence of angiographic success of PTCA, possibly because of changes in the loading condition. Coronary artery stenosis measurements and 1/Tmn failed to correlate with the left ventricular function. Given the difficulties in routine application of the analysis of time-density curves, the measurement of minimal luminal diameter remains a more practical assessment of the results of the intervention. However, the improvement of myocardial perfusion may give more information than coronary artery dimensions of the early recovery of left ventricular function.

Clinical outcome of deferring angioplasty in patients with normal translesional pressure-flow velocity measurements

OBJECTIVES

The objective of this study was to determine the feasibility, safety and outcome of deferring angioplasty in patients with angiographically intermediate lesions that are found not to limit flow, as determined by direct translesional hemodynamic assessment.

BACKGROUND

The clinical importance of some coronary stenoses of intermediate angiographic severity frequently requires noninvasive stress testing. Direct translesional pressure and flow measurements may assist in clinical decision making in patients with such stenoses.

METHODS

Translesional spectral flow velocity (Doppler guide wire) and pressure data were obtained in 88 patients for 100 lesions (26 single-vessel and 74 multivessel coronary artery lesions) with quantitative angiographic coronary narrowings (mean +/- SD diameter narrowing 54 +/- 7% [range 40% to 74%]). Target lesion angioplasty was prospectively deferred on the basis of predetermined normal values, defined as a proximal/distal velocity ratio < 1.7 or a pressure gradient < 25 mm Hg, or both. Patients were followed up for 9 +/- 5 months (range 6 to 30).

RESULTS

In the deferred angioplasty group, translesional velocity ratios were similar to those of a normal reference group (mean 1.1 +/- 0.32 vs. 1.3 +/- 0.55) and significantly lower than those of a reference cohort of patients who had undergone angioplasty (2.27 +/- 1.2, p < 0.05). The mean translesional pressure gradient in the deferred angioplasty group was also lower than that in the angioplasty group (10 +/- 9 vs. 45 +/- 22 mm Hg, p < 0.001). At follow-up in the deferred angioplasty group, four, six, zero and two patients, respectively, had had subsequent angioplasty, coronary artery bypass graft surgery or myocardial infarction or had died. In one patient, death was related to angioplasty of a nontarget artery lesion, and one patient with multivessel disease had a cardiac arrest due to ventricular fibrillation 12 months after lesion assessment. Among the 10 patients requiring later angioplasty or coronary artery bypass grafting, only six procedures were performed on target arteries. No patient had a complication of translesional flow or pressure measurements.

CONCLUSIONS

These data demonstrate the safety, feasibility and clinical outcome of deferring angioplasty of coronary artery narrowings associated with normal translesional coronary hemodynamic variables. Given the practice of performing angioplasty without ischemic testing or when testing is inconclusive, translesional hemodynamic data obtained at diagnostic catheterization can identify patients in whom it is safe to postpone angioplasty.

Measurements of human coronary vascular impedance

The aim of this study was to develop a method of measuring human coronary circulation impedance in a clinical setting. The authors measured coronary flow reserve (CFR) in 27 patients with chest pain and normal coronary arteries. A Judkins-style, 8F Doppler-tipped angiographic catheter was positioned in the left coronary ostium. Resting coronary flow velocity (RFV) and response to a hyperemic 12 mg intracoronary dose of papaverine (PFV) were measured. The signals were recorded by a recorder connected to a microprocessor with analogue-to-digital converter and a maths coprocessor. Using this the authors could obtain values for impedance at RFV (IR) and at PFV (IP). The CFR was defined as the ratio: PFV/RFV. An impedance index (II) was obtained as the ratio of coronary vascular impedance at peak hyperemia to the impedance at rest. The CFR was 3.2 +/- 1.2 and the II was 0.33 +/- 0.11. There was a strong inverse correlation between the CFR and the II (r = -0.9). The authors conclude that this new approach may allow a further insight into the coronary pathophysiology and may become useful in clinical cardiology, eg, in the assessment of heart transplant and Syndrome X patients.

Doppler flow velocity measurements during coronary angioplasty

In addition to further studies using Doppler catheters to assess blood flow velocity during coronary angioplasty this study intends to evaluate the functional significance of coronary stenoses and to estimate their hemodynamic relevance prior to and after percutaneous transluminal coronary angioplasty (PTCA). Diameters of coronary artery stenoses were quantified by means of the cardiovascular angiographic analysis system (CAAS) both prior to and following successful PTCA in 37 patients. During coronary artery angioplasty a 12 M:Hz 0.018-in. Doppler-tipped guidewire was used to measure prestenotic and poststenotic parameters of coronary artery flow velocity both prior to and following PTCA. The minimal stenosis diameter was raised from 1.01 +/- 0.58 to 1.76 +/- 0.73 mm (P < 0.0001), the percent diameter stenosis decreased from 63 +/- 11 to 35 +/- 6% (P < 0.0001). Prestenotic average (APV) and maximum peak velocity (MPV), peak velocity integral (PVI), average systolic (ASPV) and diastolic (ADPV) peak velocity, systolic (SPVI) and diastolic (DPVI) peak velocity integral, and diastolic/systolic velocity ratio showed--in contrast to further studies--a considerably significant difference (P < 0.05), whereas poststenotic Doppler data (APV, MPV, PVI, ASPV, DSPV, SPVI, DPVI, DSVR) differed highly significantly (P < 0.0001) prior to and following PTCA. Prestenotic and poststenotic measurements of coronary artery flow velocity differed significantly before and after PTCA and offer the potential for estimating both the hemodynamic relevance of coronary artery stenoses and success of PTCA.

Slope of the instantaneous hyperemic diastolic coronary flow velocity-pressure relation. A new index for assessment of the physiological significance of coronary stenosis in humans

BACKGROUND

Coronary flow reserve (CFR), the functional index of stenosis severity more frequently used in the catheterization laboratory, is greatly affected by the hemodynamic conditions at the time of measurement and cannot be applied in the immediate assessment of the outcome of coronary interventions. The aim of the present study was to establish the feasibility and reproducibility of the assessment of the slope of the instantaneous diastolic relation between coronary flow velocity and aortic pressure during maximal hyperemia (IHDVPS) using a spectral analysis of the intracoronary Doppler signal, to assess the sensitivity and specificity of this index in the detection of flow-limiting coronary stenoses in comparison with CFR, and to study the possibility of determining the zero-flow pressure from the intercept of the velocity-pressure relation on the pressure axis during a controlled cardiac arrest.

METHODS AND RESULTS

The instantaneous peak coronary flow velocity measured after intracoronary papaverine with a Doppler guidewire was plotted against the simultaneously measured aortic pressure, and the slope of the velocity-pressure relation in the phase of progressive diastolic velocity decrease was calculated during four consecutive beats. In nine normal arteries, a controlled diastolic cardiac arrest was induced by an intracoronary bolus injection of 3 mg adenosine. The IHDVPS could be assessed in 79 of 95 patients (83%), with a moderate intraobserver variability (0.4 +/- 11% after independent selection of different beats during maximal hyperemia). The IHDVPS showed no significant correlation with heart rate, mean diastolic aortic pressure, type of vessel studied, and cross-sectional area at the site of the velocity recording. The IHDVPS was significantly lower in arteries with > or = 30% diameter stenosis than in normal or near-normal arteries (0.71 +/- 0.48 versus 1.73 +/- 0.80 cm.s-1.mm Hg-1, P < .0000002). In the stenosis group, both IHDVPS and CFR were significantly correlated with the minimal luminal cross-sectional area (r = .46, P < .05 and r = .62, P < .002, respectively). The study of the velocity-pressure relation during long diastolic pauses showed a curvilinear relation between velocity and pressure in the lower pressure range, with an upward concavity to the velocity axis and no intercept with the pressure axis in most cases.

CONCLUSIONS

The IHDVPS can distinguish between arteries with and without coronary stenoses and has a significant inverse correlation with the severity of the stenosis. Under the stable hemodynamic conditions of this study, the IHDVPS and CFR had similar sensitivities and specificities in distinguishing normal and stenotic vessels and demonstrated similar correlation with minimal luminal cross-sectional area. The curvilinearity of the velocity-pressure relation during long diastolic pauses, possibly due to a significant reduction of luminal cross-sectional area at low pressures, complicates the use of the flow velocity-pressure relation for the assessment of the zero-flow pressure.

Coronary vasoconstriction after percutaneous transluminal coronary angioplasty is attenuated by antiadrenergic agents

BACKGROUND

Vasoconstriction occurs after percutaneous transluminal coronary angioplasty (PTCA) along the dilated vessel. The vasomotor changes, initiated by the mechanical stretch of the stenotic region, are thought to be due to various mechanisms but whether the sympathetic nervous system plays a role in this phenomenon remains unknown.

METHODS AND RESULTS

Quantitative angiography (ARTREK) was performed in 45 patients undergoing an epicardial vessel PTCA for a stenosis of 76 +/- 1% (1) in basal conditions, (2) after PTCA, and (3) 30 minutes after PTCA (vasoconstriction). In 14 control patients, the same measurements were obtained up to 60 minutes after PTCA. Coronary diameters were measured along the PTCA vessel at the narrowest stenosis level and at a level peripheral to stenosis. In 36 patients two diameters were also measured at a proximal segment and at a distal segment along a nonmanipulated vessel. Thirty minutes after PTCA the dilated segment underwent a -31 +/- 2% (mean +/- SEM, ANOVA, P < .05) reduction in diameter when compared with PTCA values, and the segment peripheral to stenosis showed a reduction of -17 +/- 2% (P < .05). In all patients a significant vasoconstriction also was observed along the control vessel (proximal segment, -14 +/- 3%; P < .05 versus basal; and distal segment, -17 +/- 2%). At the time of maximal vasoconstriction (30 minutes after PTCA), the patients (treatment groups) received (1) 18 micrograms/kg IC phentolamine (Phe, n = 7), (2) 14 micrograms/kg IC yohimbine (YO, n = 7), (3) 16 micrograms/kg IC propranolol (Pro) followed by 18 micrograms/kg IC phentolamine (Pro+Phe, n = 7), and (4) 0.2 mg/kg IC bretylium (Bre, n = 10). In 14 patients (control groups) an intracoronary injection of warm saline was given. After drug injections, angiograms were repeated at 5-minute intervals for 20 minutes and ended after a 300-micrograms intracoronary trinitroglycerin injection. At stenosis level, Phe and Bre counteracted vasoconstriction, inducing a dilatation of +19 +/- 3% and +22 +/- 6%, respectively, while Pro+Phe caused a dilatation of +16 +/- 9% above the PTCA values (P < .05 versus PTCA). YO only partially reversed vasoconstriction (from -33 +/- 4% to -12 +/- 4%, P = NS versus PTCA). At peripheral-to-stenosis level, vasoconstriction was abolished by Phe (+26 +/- 7%, P < .05 versus basal), while it was still present after Pro+Phe (-23 +/- 2%) and Bre (-18 +/- 4%). In addition, Phe and Bre dilated the control vessel at the proximal segment (+17 +/- 6% and +8 +/- 4%, respectively, P < .05 versus basal), while YO and Pro+Phe only counteracted vasoconstriction (from -15 +/- 3% to +7.6 +/- 1% and from -16 +/- 3% to +4 +/- 5%, respectively, P = NS versus basal). At the distal segment only Phe produced a vasodilatation of +23 +/- 1%; YO counteracted constriction (from -16 +/- 2% to +9 +/- 6%, P < .05 versus basal), whereas after Pro+Phe and Bre, the vasoconstriction persisted.

CONCLUSIONS

The mechanical stretch and ischemia caused by balloon inflation induced vasoconstriction mediated by alpha-adrenergic receptors (mainly alpha 1), overcoming a beta-mediated dilatation. The use of different antiadrenergic drugs showed that Phe counteracts post-PTCA vasoconstriction, and the simultaneous use of alpha- and beta-receptor blocking agents (Pro+Phe and Bre) reveals the presence of a peripheral, predominant beta-mediated dilatation. The presence of vasoconstriction also along the control vessels not branching from the stretched ramus provides evidence for the existence of neural sympathetic vasoconstrictor reflexes.

Digital angiographic assessment of the physiological changes to the regional microcirculation induced by successful coronary angioplasty

BACKGROUND

Impulse response analysis of digital coronary angiographic images calculates a parameter known as the mean transit time of the microcirculation (Tmicro). This has been shown to accurately assess the regional microcirculatory response to proximal stenosis in relation to flow. Our goal was to apply impulse response analysis to patients undergoing successful angioplasty and to quantify the induced physiological changes with respect to quantitative angiographic measurements of stenosis dimensions.

METHODS AND RESULTS

We studied 24 patients before and after successful single-vessel percutaneous transluminal coronary angioplasty (PTCA). Minimal luminal stenosis area was increased from 0.9 +/- 0.6 before PTCA to 4.1 +/- 1.3 mm2 after PTCA (P < .0001). In all patients this was accompanied by an increase in the inverse of Tmicro (Tmicro-1), from 8.5 +/- 3.0 to 26.5 +/- 9.0 min-1 (P < .0001) with a linear correlation between Tmicro-1 and minimal luminal stenosis area (r = .73; SEE = 7.74). Stenosis flow reserve, estimated by integration of stenosis dimensions, increased in all patients from 1.8 +/- 1.0 to 4.5 +/- 0.4 after PTCA (P < .01). A comparison of Tmicro-1 with stenosis flow reserve revealed a nonlinear relation. In 16 patients undergoing PTCA of the left anterior descending or circumflex artery, contrast injections into the left main stem allowed simultaneous measurements of Tmicro-1 in the adjacent, nonstenotic artery. Adjacent artery Tmicro-1 did not change after PTCA (25.8 +/- 6.2 compared with 25.6 +/- 6.8 min-1 before PTCA; P = NS); moreover, Tmicro-1 of the dilated artery measured after PTCA was equivalent to the nonstenotic adjacent artery, indicating normalization of microcirculatory responses.

CONCLUSIONS

These data suggest that Tmicro-1 determined by digital angiographic impulse response analysis of a single contrast injection under resting flow conditions may be a practical method to assess the regional microcirculatory response to changes in stenosis severity effected by coronary angioplasty.

Coronary flow velocity during coronary angioplasty in regions of myocardial infarction

In patients undergoing angioplasty for angina after myocardial infarction, patterns of post-stenotic coronary blood flow velocity depend not only on satisfactory dilation of the flow-limiting lesion, but also on the vasoregulatory capacity of infarcted myocardium. The case examples demonstrate both normal and persistently abnormal flow velocity patterns following successful coronary angioplasty for post-infarction ischemia. Recognition of collateral flow patterns, easily available using the Doppler angioplasty guidewire, may provide valuable information predicting the viability of post-infarcted myocardium and the resolution of abnormal distal coronary flow patterns.

Is coronary flow reserve in response to papaverine really normal in syndrome X?

BACKGROUND

An impaired coronary flow reserve in syndrome X has been demonstrated by many studies. Recently, however, a normal coronary flow reserve in response to papaverine was reported, but the number of patients in these studies was small. The aim of this study was to investigate whether coronary flow reserve in response to intracoronary papaverine is really impaired in syndrome X.

METHODS AND RESULTS

We investigated 53 syndrome X patients (typical angina, a positive exercise test, and completely normal coronary arteries on angiography) and 26 heart transplant patients with normal coronary arteries (control group). All antianginal medications were stopped 48 hours before the study. A 3.6F intracoronary Doppler catheter was positioned in the proximal left anterior descending coronary artery and was connected to a Millar velocimeter. The coronary blood flow velocity at rest and in response to a hyperemic dose of papaverine was measured. Coronary flow reserve was defined as the ratio of hyperemic coronary blood flow velocity in response to papaverine and resting coronary blood flow velocity. The coronary flow reserve (mean +/- SD) in the syndrome X group was 2.72 +/- 1.39. The coronary flow reserve in the control group was significantly higher at 5.22 +/- 1.26 (P < .01). In both groups there was no significant difference in the heart rate or the mean arterial pressure during the study.

CONCLUSIONS

Our study shows that coronary flow reserve in response to intracoronary papaverine is impaired in syndrome X patients.

Restoration of coronary blood flow in severely narrowed and chronically occluded coronary arteries before and after angioplasty: implications regarding restenosis

The restenosis rate after recanalization of chronic totally occluded coronary arteries is high. This may be due to a competitive flow or a low coronary flow velocity. This study was designed to assess differences in coronary blood flow velocity between severely narrowed and occluded arteries before and after successful percutaneous transluminal coronary angioplasty. Thirty-five patients were studied including 12 with an occluded vessel (group 1) and 23 with a stenosis (group 2). Rest and peak hyperemic (papaverine) coronary blood flow velocities were measured. Before successful percutaneous transluminal coronary angioplasty, velocity was lower in occlusions than in stenoses (3.8 +/- 2.1 vs 7.9 +/- 4.8 cm/sec; p < 0.02), whereas resistance was higher (31.7 +/- 20.8 vs 13.7 +/- 7.0 mm hg/cm/sec, respectively; p = 0.0009). There was no significant difference in vasodilator reserve between the two groups. After successful percutaneous transluminal coronary angioplasty, the velocity increased in both groups and the resistance index decreased. Velocity and resistance were similar in the two groups. The vasodilator reserve did not change after the procedure. It was concluded that the coronary flow velocity achieved after successful recanalization of chronic totally occluded arteries is similar to that observed after dilation of stenoses. These results do not support the hypothesis that the high rate of restenosis in recanalized chronically occluded vessels is due to differences in post-percutaneous transluminal coronary angioplasty blood flow velocity.

Effect of transcutaneous electrical nerve stimulation on coronary blood flow

BACKGROUND

Although neurostimulation has been shown to be of benefit in angina pectoris, the exact mechanism of its action is not clear. This study was performed to examine the effect of transcutaneous electrical nerve stimulation on coronary blood flow.

METHODS AND RESULTS

The effect of transcutaneous electrical nerve stimulation was studied in 34 syndrome X patients (group 1), 15 coronary artery disease patients (group 2), and 16 heart transplant patients (group 3). Coronary blood flow velocity (CBFV) in the left coronary system was measured at rest and after a 5-minute stimulation period with a Judkins Doppler. There was a significant increase in the resting CBFV in group 1 (from 6.8 +/- 4.1 to 10.5 +/- 5.7 cm/s, P < .001) and group 2 (from 6.8 +/- 4.1 to 10.5 +/- 5.7 cm/s, P < .001). However, there was no significant change in the resting CBFV in group 3. There were no significant changes in the coronary arterial diameters as a result of neurostimulation. There was a significant decrease in the epinephrine levels in group 1 (from 79.6 +/- 17.8 to 58.5 +/- 17.5 ng/L, P = .01) and group 2 (from 102.2 +/- 27.2 to 64.1 +/- 19.1 ng/L, P = .01).

CONCLUSIONS

Transcutaneous electrical nerve stimulation can increase resting coronary blood flow velocity. The findings suggest that the site of action is at the microcirculatory level and that the effects may be mediated by neural mechanisms.

Validation of volumetric flow measurements by means of a Doppler-tipped coronary angioplasty guide wire

We used an in vitro model to validate volumetric flow measurements obtained with an 0.018-inch angioplasty guidewire with a 12 MHz transducer mounted on its tip. By using a modified two-head roller pump device, flow was adjusted incrementally from a minimum of 90 ml/min to a maximum of 550 ml/min. Flow was measured with the Doppler guide wire in tubing ranging from 1.9 mm to 6.0 mm internal diameter, as the product of the spectral Doppler velocity integral and the cross-sectional area of the tubing, over a 1-minute period. It was an excellent correlation between the Doppler calculated flow rates and actual flow, regardless of tubing diameter (r = 0.99). These results suggest that the Doppler spectral output of this device might be accurately applied to estimates of volumetric flow in human coronary arteries.

Noninvasive assessment of coronary flow dynamics before and after coronary angioplasty using transesophageal Doppler

Recent invasive studies using intracoronary Doppler catheters or guide wires reported improved coronary flow dynamics after successful percutaneous transluminal coronary angioplasty. Transesophageal Doppler enables the measurement of coronary flow velocities within the left anterior descending artery. The present study was designed to test: (1) whether transesophageal Doppler may detect coronary flow velocity changes in patients undergoing angioplasty for left anterior descending artery stenosis, and (2) whether this technique may help to evaluate non-invasively the results of the procedure. Twenty-three patients undergoing angioplasty of the left anterior descending artery were studied by transesophageal Doppler before and < or = 24 hours after the interventional procedure. Coronary flow velocities were measured in the proximal part of the left anterior descending artery with the use of pulsed Doppler guided by color flow imaging. The degree of stenosis was measured by computerized quantitative coronary arteriography. Coronary flow velocity signals were successfully obtained in 19 of 23 patients (83%). In 16 successful angioplasty procedures, peak diastolic velocity increased from 37 +/- 14 cm/s before angioplasty to 51 +/- 16 cm/s after (p = 0.0001). In the 3 patients in whom angioplasty was unsuccessful, transesophageal Doppler showed no significant increase in peak diastolic coronary flow velocity. In a total of 19 angioplasty procedures, a good linear relation was found between the percent changes in coronary flow diastolic velocity and the reduction in the degree of stenosis (r = 0.85; p = 0.0001). All patients with > 20% increase in peak diastolic velocity had > 40% stenosis reduction.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantitative demonstration of dipyridamole-induced coronary steal and alteration by angioplasty in man: analysis by simultaneous, continuous dual Doppler spectral flow velocity

In the course of studying the effects of coronary angioplasty on branch vessel flow using two Doppler flow velocity guidewires, we quantitated simultaneous blood flow responses proximal and distal to a stenosis. The alterations of flow documented a horizontal epicardial steal induced during dipyridamole hyperemia, hyperemic flow reversal by intravenous aminophylline, and subsequent normalization of distal hyperemia after endoluminal enlargement by successful angioplasty. The quantitative physiology of the patient described here confirms one postulated mechanism of abnormal myocardial perfusion stress scintigraphy. Continuous dual flowire spectral coronary flow determinations appear to be a valuable method in verifying postulated mechanisms of various pharmacologic and mechanical stimuli influencing coronary blood flow in patients with atherosclerotic coronary artery disease.

Assessing the hemodynamic significance of coronary artery stenoses: analysis of translesional pressure-flow velocity relations in patients

OBJECTIVES

The purpose of this study was to examine the relation among the angiographic severity of coronary artery lesions, coronary flow velocity and translesional pressure gradients.

BACKGROUND

Determination of the clinical and hemodynamic significance of coronary artery stenoses is often difficult and inexact. Angiography has been shown to be an imperfect tool for determining the physiologic significance of eccentric or irregular coronary lumen narrowing.

METHODS

Using a 0.018-in. (0.046 cm) intracoronary Doppler-tipped angioplasty guide wire, spectral flow velocity data both proximal and distal to coronary stenoses were compared with translesional pressure gradient measurements and angiographic data obtained during cardiac catheterization in 101 patients. There were 17 patients with normal angiographic findings and 84 with coronary artery disease, with lesions ranging from 28% to 99% diameter narrowing. Patients with coronary disease were assigned to two groups on the basis of translesional gradients at rest. Group A (n = 56) had gradients < 20 mm Hg, and Group B (n = 28) had gradients > or = 20 mm Hg.

RESULTS

Proximal average peak velocity, diastolic velocity integral and total velocity integral were slightly but statistically lower in Group A; however, the distal average peak velocity and diastolic and total velocity integrals were all markedly (all p < 0.01) decreased in patients with gradients > or = 20 mm Hg (Group B). In addition, the ratio of proximal to distal total flow velocity integral was higher in Group B (2.4 +/- 1.0) than in group A (1.1 +/- 0.3, p < 0.001). There was a strong correlation between translesional pressure gradients and the ratios of the proximal to distal total flow velocity integrals (r = 0.8, p < 0.001), with a weaker relation between quantitative angiography and pressure gradients (r = 0.6, p < 0.001). In angiographically intermediate stenoses (range 50% to 70%), angiography was a poor predictor of translesional gradients (r = 0.2, p = NS), whereas the flow velocity ratios continued to have a strong correlation (r = 0.8, p < 0.001). Only two patients with a proximal/distal total flow velocity ratio < 1.7 had a translesional gradient > 30 mm Hg. Both patients had a very proximal lesion in a nonbranching right coronary artery.

CONCLUSIONS

These data demonstrate that in branching human coronary arteries, a close relation exists between translesional hemodynamics and distal coronary flow velocity. Translesional coronary flow velocity is a new and easily applicable method for determining the hemodynamic significance of coronary artery stenoses that is superior to angiography and can be applied at the time of diagnostic catheterization. These data will provide a rational approach to making decisions on the use of coronary interventional techniques when angiographic findings are questionable.

Endothelium dependent and independent responses in coronary artery disease measured at angioplasty

OBJECTIVE--To investigate the effects of substance P and papaverine, two drugs that increase coronary blood flow by different mechanisms, on vasomotion in stenotic coronary arteries at percutaneous transluminal coronary angioplasty (PTCA). DESIGN--Coronary blood flow responses to substance P and papaverine were measured in stenotic coronary arteries at the time of PTCA with quantitative angiography and a Doppler flow probe. SETTING--A cardiothoracic referral centre. PATIENTS--15 patients undergoing elective PTCA of a discrete epicardial coronary artery stenosis. INTERVENTIONS--Pharmacological coronary flow reserve was determined with papaverine 5-10 minutes before and after successful PTCA. Endothelium dependent responses to 2 minute infusions of substance P (10-15 pmol.min-1) were assessed immediately before PTCA. MAIN OUTCOME MEASURES--Coronary blood flow responses and changes in epicardial coronary artery area at stenotic, proximal, and distal sites with papaverine and substance P. RESULTS--Stenotic sites dilated with papaverine before PTCA (17.7%(6.9%) (mean (SEM)) area increase, p < 0.05 v baseline). Substance P dilated stenotic sites (16.8%(5.7%) area increase, p < 0.05) and proximal (14.3%(5.4%), p < 0.05) and distal sites (41.7%(9.3%), p < 0.005). Coronary flow reserve increased but did not reach normal values after PTCA (2.3(0.4) before PTCA v 3.0(0.4) after PTCA, p < 0.05) and was associated with an increase in peak flow with papaverine. Angioplasty did not alter baseline flow. After PTCA papaverine caused significant vasoconstriction at the stenotic site (-13.6%(4.3%) area decrease, p < 0.05). There was a negative correlation (r = -0.68, p < 0.05) between the dilator response with papaverine before PTCA and the constrictor response after PTCA. CONCLUSIONS--Substance P causes endothelium dependent dilatation in atheromatous coronary arteries, even at sites of overt atheroma. The cause of the paradoxical constrictor response to papaverine after PTCA is uncertain, but unopposed flow mediated vasoconstriction (the myogenic response) after balloon induced endothelial denudation may be one of several contributory factors.

Effect of hyperventilation and mental stress on coronary blood flow in syndrome X

OBJECTIVES

To assess the effect of hyperventilation and mental stress on coronary blood flow and symptom production in patients with syndrome X.

DESIGN

A prospective study. Hyperventilation and mental stress tests were performed on the ward and were repeated in the cardiac catheter laboratory where coronary blood flow velocity was also measured with an intracoronary Doppler catheter in the left anterior descending coronary artery. Oesophageal manometry studies were also performed.

PATIENTS

29 patients with syndrome X (typical anginal chest pain, a positive exercise test, and normal coronary angiogram).

SETTING

A regional cardiothoracic centre.

RESULTS

Hyperventilation produced typical chest pain in 16 patients on the ward. 13 patients experienced their typical chest pain with mental stress test 5. Ten patients experienced chest pain with both hyperventilation and mental stress tests. This pattern was reproduced exactly when the tests were repeated in the cardiac catheter laboratory. Hyperventilation produced a significant increase in the rate-pressure product during ward and laboratory testing. There was, however, no significant change in the rate-pressure product on mental stress tests. The mean (SEM) coronary flow velocity decreased significantly on hyperventilation in the catheter laboratory from 10.0 (0.92) cm/s to 5.9 (0.72) cm/s (p < 0.001). There was also a significant reduction in the mean (SEM) coronary blood flow velocity on mental stress tests from 9.8 (0.86) cm/s to 7.4 (0.6) cm/s (p < 0.001). This reduction in flow velocity occurred in the absence of any changes in diameter of the left anterior descending artery. Further analysis showed that the coronary flow velocity was reduced significantly in only that group of patients in which hyperventilation and mental stress provoked chest pain. There was a significant increase in the arterial concentrations of noradrenaline on both hyperventilation and mental stress testing. Oesophageal manometry showed abnormalities in 17% of patients.

CONCLUSIONS

Both hyperventilation and mental stress can produce chest pain in patients with syndrome X and this is associated with a reduction in coronary blood flow velocity. The results of this study suggests that this reduction in coronary flow occurs as a result of increased microvascular resistance.

Coronary flow velocity dynamics in normal and diseased arteries

Distal coronary flow velocity measurements were previously limited to open heart or experimental procedures. Unlike previous Doppler catheter techniques, a Doppler angioplasty flow wire permits flow velocity measurements in both the proximal and distal segments of normal and diseased coronary arteries. In order to determine the potential clinical application of the Doppler flow wire, we performed baseline and hyperemia flow velocity measurements in proximal and distal segments of 20 angiographically normal arteries (right coronary = 8; left circumflex = 7; left anterior descending = 5) and 29 significantly stenosed arteries. All 3 normal coronary arteries had a diastolic-predominant pattern in both proximal and distal segments; the right coronary artery showed significantly less diastolic predominance. The coronary vasodilator reserve was similar in all three normal coronary arteries, and in the proximal and distal arterial segments. Abnormal arteries had significantly lower coronary vasodilator reserve (normal vs abnormal, 2.3 +/- 0.8/1.6 +/- 0.7; p < 0.02). Normal arteries had preservation of velocity parameters in the distal segments; abnormal arteries had a significant decrease in distal velocity parameters. The proximal-to-distal velocity ratio was thus significantly higher in abnormal arteries (2.4 +/- 0.7 vs 1.1 +/- 0.2; p < 0.001). The coronary vasodilator reserve in proximal and distal arteries--in addition to the proximal to distal velocity ratio--may provide functional and hemodynamic data complementary to coronary angiography in the assessment of coronary artery stenosis.

Coronary artery flow monitoring following coronary interventions

Technologic innovations have made it possible to measure coronary artery blood flow in awake patients. Both flow velocity as well as flow reserve can be assessed. In particular, the period of time immediately following coronary interventions offers a unique opportunity to study important features of coronary flow behavior. In 22 patients, coronary flow reserve was measured before and after an intervention, either angioplasty or atherectomy, using a 0.018-in Doppler guidewire (Flowire). The minimum lumen diameter (MLD) was increased from 1.0 +/- 0.4 to 1.7 +/- 0.4 mm, while coronary flow velocity increased significantly, rising from 29 +/- 13 to 39 +/- 14 cm/sec (p < 0.025). The maximum hyperemic velocity also increased, from 44 +/- 16 to 69 +/- 21 cm/sec. Using only the preintervention or postintervention values, the flow reserve ratio was 1.53 +/- 0.4 prior to intervention and 1.84 +/- 0.5 after intervention (p = nonsignificant). However, the post-intervention value may have been artifactually reduced by the fact that both resting as well as hyperemic velocities increased. When the post-intervention flow reserve ratio was recalculated, using the preintervention resting value, flow reserve ratio was seen in increase from 1.53 +/- 0.4 to 2.73 +/- 1.2 (p < 0.001). Measurements of coronary flow in the postintervention period also revealed several interesting phenomena. Spasm of a coronary artery was documented, and its resolution in response to intracoronary nitroglycerin was observed. Elastic recoil following angioplasty was documented by gradual decline in coronary flow over 30 minutes.(ABSTRACT TRUNCATED AT 250 WORDS)

Applications of coronary flow velocity during angioplasty and other coronary interventional procedures

Previous studies utilizing Doppler catheters to assess blood flow immediately following coronary artery interventions have failed to demonstrate significant improvement in proximal coronary artery velocities or vasodilator reserve. Measurement of blood flow velocity, flow reserve, and the phasic diastolic/systolic velocity ratio in the distal coronary artery has been performed following various interventional procedures utilizing a low profile (.018 in) Doppler angioplasty guidewire. Following balloon angioplasty in 38 patients, average peak velocity increased significantly from 19 +/- 12 to 35 +/- 16 cm/sec in the distal coronary artery. The diastolic/systolic flow ratio improved from 1.3 +/- 0.5 to 1.8 +/- 0.5 and coronary flow reserve remained unchanged. Similar improvement in distal mean velocities (200%) versus proximal mean velocities (90% increase), and improvement in phasic velocity patterns, total velocity integral, and peak diastolic velocity were also noted in a separate study of 29 patients, before and after balloon angioplasty. Following excimer laser angioplasty in 10 patients, average peak velocity in the distal coronary artery was noted to increase from 6.3 to 13.0 cm/sec following laser alone, with a further increase to 20.6 cm/sec following adjunctive balloon angioplasty. The diastolic/systolic flow ratio increased from a mean value of 1.1 to 2.0 following laser recanalization, with a further increase to 2.9 following adjunctive balloon angioplasty. Following directional coronary atherectomy only modest improvement in distal average peak velocity was noted (24.7 to 31.2 cm/sec), with no significant change in diastolic/systolic velocity ratio (1.78 vs 2.04) immediately following the procedure. Measurement of distal flow velocity parameters performed immediately following coronary interventions may prove useful in assessing the hemodynamic result of these interventions and may prove useful in clinical decision making.

Intracoronary pressure and flow velocity with sensor-tip guidewires: a new methodologic approach for assessment of coronary hemodynamics before and after coronary interventions

The use of miniaturized pressure and velocity sensors mounted on angioplasty guidewires allows the simultaneous measurement of coronary blood flow velocity and transstenotic pressure gradient, 2 parameters that, combined, should perfectly characterize stenosis hemodynamics. The aim of this article is assessment of the changes in coronary blood flow velocity observed with a Doppler-tipped angioplasty guidewire in 35 patients undergoing balloon angioplasty. We also report our initial experience in 16 patients with the combined use of sensor-tip pressure and Doppler guidewires, and we discuss the application of new methodologic approaches for the study of the coronary circulation allowed by these techniques, such as the instantaneous assessment of the flow velocity/pressure and pressure gradient/flow velocity relations. Before and after angioplasty, flow velocity measurements were obtained distal to the stenosis, both in baseline conditions and after intracoronary injection of 8-12.5 mg of papaverine. The Doppler guidewire was left in place during the dilation procedure and the Doppler signal was continuously recorded during balloon inflation and after deflation to monitor the development of collateral flow, the restoration of flow after balloon deflation, the phase of postocclusive reactive hyperemia, and, incidently, the development of flow-limiting complications. Merits and pitfalls of several flow velocity parameters (average peak velocity, coronary flow velocity reserve, diastolic/systolic velocity ratio), as well as of parameters derived from the combination of pressure and velocity measurements (transstenotic pressure gradient/flow velocity relation and instantaneous diastolic hyperemic flow velocity/pressure relation) were evaluated in 35 patients with, and 37 without, significant coronary stenoses.(ABSTRACT TRUNCATED AT 250 WORDS)

Delayed recovery of coronary resistive vessel function after coronary angioplasty

OBJECTIVES

The aim of this study was to use Doppler catheterization and sequential dynamic positron emission tomography (PET) to investigate the role and time course of abnormal coronary resistive vessel function in the impairment of the coronary vasodilator response (maximal/basal coronary blood flow) after successful coronary angioplasty.

BACKGROUND

The coronary vasodilator response may be impaired immediately after coronary angioplasty, despite successful dilation of a flow-limiting stenosis.

METHODS

Twelve men (mean age 52 +/- 10 years) with single-vessel coronary artery disease and normal left ventricular function were studied. The coronary vasodilator response to intravenous dipyridamole (0.5 mg.kg-1 over 4 min) was determined from intracoronary Doppler measurement of coronary flow velocity, before and after successful angioplasty. Basal and maximal myocardial blood flow in the angioplasty region and a normal region were determined in nine patients wtih positron emission tomography with H2(15)0 at 1 day (PET1), 7 days (PET2) and 3 months (PET3) after angioplasty.

RESULTS

The coronary vasodilator response, measured by Doppler catheterization, was similar before and immediately after angioplasty, 1.63 +/- 0.41 and 1.62 +/- 0.55, respectively (p = NS). After angioplasty, in seven of nine patients without restenosis, basal myocardial blood flow at PET1, PET2 and PET3 was 0.98 +/- 0.16, 0.94 +/- 0.09 and 0.99 +/- 0.13 ml.min-1 x g-1, respectively, in the remote region and 1.19 +/- 0.23 (p < 0.01 vs. remote region), 1.17 +/- 0.19 (p < 0.01 vs. remote region) and 1.10 +/- 0.08 ml.min-1 x g-1 (p = NS vs. remote region), respectively, in the angioplasty region. Myocardial blood flow after dipyridamole at PET1, PET2 and PET3 was 3.04 +/- 0.68, 3.00 +/- 0.71 and 3.00 +/- 0.60 ml.min-1 x g-1, respectively, in the remote region and 2.11 +/- 0.80 (p < 0.01 vs. remote region), 2.28 +/- 0.73 (p = NS vs. remote region) and 3.06 +/- 0.86 ml.min-1 x g-1 (p = NS vs. remote region), respectively, in the angioplasty region. The coronary vasodilator response at PET1, PET2 and PET3 was 3.15 +/- 0.85, 3.18 +/- 0.68 and 3.08 +/- 0.75, respectively, in the remote region and 1.80 +/- 0.68 (p < 0.01 vs. remote region), 1.94 +/- 0.49 (p < 0.01 vs. remote region) and 2.77 +/- 0.74 (p = NS vs. remote region), respectively, in the angioplasty region.

CONCLUSIONS

After successful angioplasty, basal myocardial blood flow is increased for > or = 7 days in the angioplasty region, with a reduction in the dipyridamole-induced increase in maximal myocardial blood flow for > or = 24 h after the procedure. Thus, the coronary vasodilator response is impaired for > or = 7 days after angioplasty, indicating that there is abnormal resistive vessel function in the coronary vascular bed distal to a coronary artery stenosis that persists for 7 days to 3 months.

Augmentation of coronary blood flow by intra-aortic balloon pumping in patients after coronary angioplasty

BACKGROUND

Controversy exists regarding the ability of intra-aortic balloon pumping to increase coronary blood flow in patients with obstructive coronary artery disease. To assess the effects of intra-aortic balloon pumping on coronary hemodynamics, we measured coronary blood flow velocity with a 0.018-in. Doppler-tipped angioplasty guide wire in 15 patients who received an intra-aortic balloon pump for typical clinical indications.

METHODS AND RESULTS

Intra-aortic balloon pumping augmented diastolic pressure 83 +/- 35%. In nine patients before angioplasty, peak diastolic coronary flow velocity beyond the stenosis (mean diameter narrowing, 95 +/- 7%) was 5.3 +/- 9.6 cm/sec and was unaffected by intra-aortic balloon pumping. After angioplasty, the improved coronary luminal diameter narrowing (n = 12; mean narrowing, 18 +/- 12%) was associated with increased distal diastolic flow velocity integral and peak diastolic and mean velocities (13.3 +/- 8.4 units: 36.4 +/- 18.3 and 24.0 +/- 11.4 cm/sec, respectively; all p < 0.01 versus before angioplasty), which were further augmented (36 +/- 37%, 54 +/- 49%, and 26 +/- 17%, respectively; all p < 0.01) with intra-aortic balloon pumping. Intra-aortic balloon pumping did not significantly increase the distal systolic velocity integral (10 +/- 59%) or peak systolic velocity (3 +/- 33%). Similar degrees of balloon pump augmentation of distal coronary flow velocity values were observed in five angiographically normal reference arteries in four patients.

CONCLUSIONS

These data demonstrate lack of significant flow improvement beyond most critical stenoses with intra-aortic balloon pumping and the unequivocal restoration and intra-aortic balloon pump-mediated augmentation of both proximal and distal coronary blood flow velocities after amelioration of severe coronary obstructions in patients after successful coronary angioplasty.

Enhanced coronary blood flow velocity during intraaortic balloon counterpulsation in critically ill patients

OBJECTIVES

The aim of this study was to assess coronary blood flow during intraaortic balloon counterpulsation by direct measurement.

BACKGROUND

In a majority of human studies, increased coronary blood flow during intraaortic balloon counterpulsation measured by indirect techniques has not been consistently demonstrated.

METHODS

Hemodynamic variables and coronary blood flow velocity (20-MHz Doppler-tipped catheter) data were measured in 19 patients requiring intraaortic balloon pumping for clinical indications (11 patients had acute myocardial infarction [9 with shock], 6 had unstable angina, 1 had acute mitral regurgitation and 1 was at high risk undergoing angioplasty). Hemodynamic data, mean and phasic diastolic flow velocity and velocity-time integrals (computed from digitized waveforms) were analyzed during periods of 1:1 balloon counterpulsation.

RESULTS

Intraaortic balloon pumping decreased systolic pressure (6 +/- 10%, p < 0.001) and increased diastolic pressure (80 +/- 30% from baseline, p < 0.001) without changing RR interval. Peak phasic, mean coronary flow velocity and diastolic flow velocity integral were significantly increased (115 +/- 115%, 67 +/- 61%, 103 +/- 81%, respectively, all p < 0.001) during intraaortic balloon pumping. In addition, although a wide splay of data was evident due to operator set variations in balloon inflation and deflation timing, the greater increases in diastolic flow velocity integral (DFVi) occurred in patients with basal systolic pressure < or = 90 mm Hg (% delta DFVi = 102 - 0.1.[unaugmented systolic pressure], SEE = 21.7 mm Hg, r = 0.30, p < 0.001).

CONCLUSIONS

Intraaortic balloon pumping unequivocally and significantly augments proximal coronary blood flow velocity, nearly doubling the coronary flow velocity integral in most patients. This mechanism may be a significant means of ischemia relief in hypotensive patients.

Analysis of coronary blood flow velocity dynamics in angiographically normal and stenosed arteries before and after endolumen enlargement by angioplasty

OBJECTIVES

This study was designed to assess whether the spectral waveform of coronary velocity on Doppler study is characteristically altered in the presence of significant stenosis with normalization of the spectral waveform after relief of endolumen obstruction.

BACKGROUND

Although coronary flow reserve determinations have provided physiologic information complementary to the angiographic percent diameter narrowing, flow velocity measurements have been limited to proximal arteries with inconsistent results after angioplasty. A 12-MHz Doppler guide wire permits flow velocity determination in the proximal and distal coronary artery with fast Fourier spectral analysis.

METHODS

With the Doppler guide wire, proximal arterial flow velocity and flow reserve measurements in 17 angiographically normal arteries were compared with measurements in 29 significantly stenosed arteries. Proximal and distal flow velocity measurements were also obtained before and after angioplasty of the 29 abnormal arteries. Velocity spectrum was digitized to compute peak diastolic velocity, peak systolic velocity, mean velocity, diastolic/systolic velocity ratio and first third and first half flow fraction.

RESULTS

Compared with proximal stenosed arteries, proximal normal arteries had significantly higher peak diastolic velocity (64 +/- 26 cm/s vs. 41 +/- 26 cm/s) and higher coronary vasodilator reserve (2.3 +/- 0.8 vs. 1.6 +/- 0.7). Normal arteries had higher flows in the first third and first half of the coronary cycle (46 +/- 3% vs. 39 +/- 7% and 65 +/- 2% vs. 56 +/- 10%, respectively). Before angioplasty, coronary velocity variables were significantly lower distal than proximal to the stenosis. After angioplasty, there was a greater mean increase in distal velocities (200% vs. 90% for the proximal arteries) that resulted in near equalization of proximal and distal mean velocity and a significant reduction in proximal/distal mean velocity ratio (2.4 +/- 1.7 vs. 1.2 +/- 0.4).

CONCLUSIONS

Before angioplasty, abnormal coronary flow velocity dynamics are more marked distal than proximal to the stenosis. Greater increase in coronary flow velocities in the distal circulation after relief of endolumen obstruction results in a significant reduction in the proximal/distal flow velocity ratio. Thus, normalization of Doppler-derived flow velocity variables with marked reduction of the proximal/distal flow velocity ratios parallels angiographic success and may prove useful as an additional end point measurement in interventional cases with questionable angiographic findings.

Alterations of phasic coronary artery flow velocity in humans during percutaneous coronary angioplasty

BACKGROUND AND OBJECTIVES

Studies using Doppler catheters to assess blood flow velocity and vasodilator reserve in proximal coronary arteries have failed to demonstrate significant improvement immediately after coronary angioplasty. Measurement of blood flow velocity, flow reserve and phasic diastolic/systolic velocity ratio performed distal to a coronary stenosis may provide important information concerning the physiologic significance of coronary artery stenosis. This study was designed to measure these blood flow velocity variables both proximal and distal to a significant coronary artery stenosis in patients undergoing coronary angioplasty.

METHODS

A low profile (0.018-in.) (0.046-cm) Doppler angioplasty guide wire capable of providing spectral flow velocity data was used to measure blood flow velocity, flow reserve and diastolic/systolic velocity ratio both proximal and distal to left anterior descending or left circumflex coronary artery stenosis. These measurements were made in 38 patients undergoing coronary angioplasty and in 12 patients without significant coronary artery disease.

RESULTS

Significant improvement in mean time average peak velocity was noted in distal coronary arteries after angioplasty (before 19 +/- 12 cm/s; after 35 +/- 16 cm/s; p less than 0.01). Increases in proximal average peak velocity after angioplasty were less remarkable (before 34 +/- 18 cm/s; after 41 +/- 14 cm/s; p = 0.04). Mean flow reserve remained unchanged after angioplasty both proximal (1.5 +/- 0.5 vs. 1.6 +/- 1; p greater than 0.10) and distal (1.6 +/- 1 vs. 1.5 +/- 0.8; p greater than 0.10) to a coronary stenosis. Before angioplasty, mean diastolic/systolic velocity ratio measured distal to a significant stenosis was decreased compared with that in normal vessels (1.3 +/- 0.5 vs. 1.8 +/- 0.5; p less than 0.01). After angioplasty, distal abnormal phasic velocity patterns generally returned to normal, with a significant increase in mean diastolic/systolic velocity ratio (1.3 +/- 0.5 vs. 1.9 +/- 0.6; p less than 0.01). Phasic velocity patterns and mean diastolic/systolic velocity ratio measured proximal to a coronary stenosis were not statistically different from values in normal vessels (1.8 +/- 0.8 vs. 1.8 +/- 0.5; p greater than 0.10) and did not change significantly after angioplasty (1.8 +/- 0.8 vs. 2.13 +/- 0.9; p greater than 0.10).

CONCLUSIONS

Flow velocity measurements may be performed distal to a coronary stenosis with the Doppler guide wire. Phasic velocity measurements made proximal to a coronary stenosis differed from those in the distal coronary artery. Both proximal and distal flow reserve measurements made immediately after angioplasty were of limited utility. Changes in distal flow velocity patterns and diastolic/systolic velocity ratio appeared to be more relevant than the hyperemic response in assessing the immediate physiologic outcome of coronary angioplasty.

Simultaneous measurement of coronary flow reserve by left anterior descending coronary artery Doppler and great cardiac vein thermodilution methods

OBJECTIVES

The objective of this study was to compare left anterior descending coronary artery Doppler blood flow velocity and great cardiac vein thermodilution blood flow measurements of coronary flow reserve and submaximal coronary vasodilation in humans.

BACKGROUND

Reported maximal coronary flow reserve values obtained with the coronary venous thermodilution method are lower than those obtained with other measurement methods.

METHODS

Thermodilution measurements of great cardiac vein flow in 11 subjects were compared with simultaneous Doppler measurements of changes in left anterior descending coronary flow velocity after intracoronary administration of papaverine, nitroglycerin, iohexol and intravenous administration of dipyridamole.

RESULTS

Coronary flow reserve (papaverine peak/rest flow ratio) was 3.7 +/- 1.7 (mean +/- SD) by the Doppler method and 2.0 +/- 0.7 by the thermodilution technique (p less than 0.001). Thermodilution flow changes were also smaller than Doppler-measured changes during submaximal vasodilation and during prolonged coronary dilation after dipyridamole administration.

CONCLUSIONS

Coronary flow reserve and submaximal flow increases measured with the thermodilution method were consistently and substantially smaller than Doppler-derived measurements. This discrepancy has important implications for the comparison of coronary flow reserve measurements performed with the use of different techniques.

The effects of ionic and nonionic radiographic contrast media on coronary hyperemia in patients during coronary angiography

The purpose of this study was to compare the differential effects of ionic, high-osmolar meglumine diatrizoate; ionic, low-osmolar ioxaglate meglumine; and nonionic, low-osmolar iohexol (all radiographic contrast agents) on coronary blood flow velocity and hyperemic responses during diagnostic coronary angiography. Coronary flow velocity and arterial pressure were measured at baseline and during maximal hyperemia after contrast media were randomly injected (4 to 6 ml into left coronary artery) in 22 patients with the use of a Judkins-style 20 MHz Doppler-tipped angiographic catheter. Contrast media-induced hyperemic responses were compared to those induced with intracoronary nitroglycerin (200 micrograms) and papaverine (10 mg). There were no significant differences in systolic, diastolic, or mean arterial pressure measurements among the three contrast agents. The increase in mean coronary flow velocity during hyperemia was 118 +/- 93%, 133 +/- 73%, and 136 +/- 86% for iohexol, ioxaglate meglumine, and diatrizoate, respectively (p = NS among agents vs 264 +/- 109% for papaverine; p less than 0.05 for all). Coronary vasodilatory reserve (calculated as the ratio of hyperemic to basal mean flow velocity) was also similar among agents. It was comparable to the coronary vasodilatory reserve with nitroglycerin (2.1 +/- 1.0 to 2.2 +/- 1.1) and significantly less than that with papaverine (3.3 +/- 2.2, p less than 0.05). These data indicate that the clinical advantages of nonionic or low-osmolar contrast media are not mechanistically related to significant attenuation of the coronary hyperemic response.

The effect of ergonovine on coronary vasodilatory reserve in patients with angiographically normal coronary arteries

Ergonovine produces physiologic coronary artery narrowing in many patients without focal coronary spasm. The effect of ergonovine-induced coronary vasoconstriction on coronary vasodilatory reserve is unknown. Therefore we studied 10 patients with atypical chest pain and angiographically normal coronary arteries. The heart rate and blood pressure were recorded continuously and coronary Doppler flow velocity was measured continuously with a 20 MHz Doppler-tipped catheter. Ergonovine caused diffuse narrowing of the vessels in all patients, with a 12% +/- 5% change in diameter of the left anterior descending coronary artery (p less than 0.001). There was a significant change in systolic (17% +/- 12% change; p less than 0.05) and mean arterial pressure (13% +/- 13% change; p less than 0.05), with no significant change in mean coronary flow velocity with ergonovine. Ergonovine also did not attenuate the maximal hyperemic response with papaverine. Thus despite an increase in myocardial demand and a decrease in caliber of conductance coronary vessels, the coronary autoregulatory flow responses were intact after the administration of ergonovine.

Temporal increase in resting coronary blood flow causes an impairment of coronary flow reserve after coronary angioplasty

Impaired coronary flow reserve immediately after coronary angioplasty may be attributed to an increase in resting coronary blood flow. To test this hypothesis we measured great cardiac venous flow (GCVF) at rest and during rapid atrial pacing before and immediately after angioplasty in 22 patients with significant narrowing of the left anterior descending artery and 12 patients (control group) with minimal narrowing. A follow-up (6 months) study was also done in seven patients. Immediately after angioplasty the coronary flow reserve (peak GCVF during pacing/resting GCVF) was not fully restored (1.5 +/- 0.36 before angioplasty, 1.76 +/- 0.42 after angioplasty, and 2.13 +/- 0.33 in the control group). Resting coronary vascular resistance (2.4 +/- 0.9 mm Hg/ml/min) was significantly decreased after angioplasty (2.0 +/- 0.8 mm Hg/ml/min), whereas coronary vascular resistance during rapid pacing was fully restored to normal. Resting hyperemia was restored 6 months later, whereas coronary vascular resistance during pacing was unaltered. In five patients, however, slight ischemic ST-T changes were observed during rapid pacing, even after successful angioplasty associated with a decrease in the lactate extraction ratio. These results indicate that the impaired coronary flow reserve immediately after angioplasty may be attributed mainly to the temporal but significant increase in resting coronary flow, although impaired coronary vascular response to augmented myocardial oxygen demand may also be partially involved.

Coronary flow reserve is impaired early after cardiac transplantation

The highest mortality rate after cardiac transplantation, at present, occurs within the first year after cardiac transplantation. The state of the coronary microcirculation soon after cardiac transplantation has not been previously assessed. We investigated the hypothesis that coronary flow reserve (CFR) is impaired in the early postoperative period after cardiac transplantation. A 3F intracoronary Doppler flow probe was inserted into the left anterior descending coronary artery and maximal coronary flow was assessed using the non-endothelial-dependent vasodilator papaverine. We compared two groups of patients: group A--13 patients studied 3 months after operation; and group B--25 patients studied at a median of 4 years after operation (range 2-8 years) without coronary occlusive disease (COD). CFR was defined as the quotient of maximum hyperaemic to resting velocity (vel). CFR was markedly impaired in group A patients compared with group B (3.3 SEM 0.3 versus 4.2 SEM 0.2, P < 0.01). No significant differences between mean resting or peak velocities, original diagnosis, age, active rejection, blood pressure, lipid levels, ischaemic time, cyclosporin levels or cytomegalovirus (CMV) status were noted. Responses to papaverine in resistance coronary vessels are impaired in the early postoperative period after cardiac transplantation. This is caused by a combination of higher resting flow and lower peak flow in the early group. This impairment of function in the coronary microcirculation may contribute to early graft dysfunction and reflect changes in vascular smooth muscle function leading to the development of COD.

Intravenous adenosine: continuous infusion and low dose bolus administration for determination of coronary vasodilator reserve in patients with and without coronary artery disease

To assess the use of adenosine as an alternative agent for determination of coronary vasodilator reserve, hemodynamics and coronary blood flow velocity were measured at rest and during peak hyperemic responses to continuous intravenous adenosine infusion (50, 100 and 150 micrograms/kg per min for 3 min) and intracoronary papaverine (10 mg) in 34 patients (17 without [group 1] and 17 with [group 2] significant left coronary artery disease), and in 17 patients (11 without and 6 with left coronary artery disease) after low dose (2.5 mg) intravenous bolus injection of adenosine. The maximal adenosine dose did not change mean arterial pressure (-10 +/- 14% and -6 +/- 12% for groups 1 and 2, respectively) but increased the heart rate (15 +/- 18% and 13 +/- 16, respectively). For continuous adenosine infusions, mean coronary flow velocity increased 64 +/- 104%, 122 +/- 94% and 198 +/- 59% and 15 +/- 51%, 110 +/- 95% and 109 +/- 86% in groups 1 and 2, respectively for each of the three doses. Mean coronary flow velocity increased significantly after 100 and 150 micrograms/kg of adenosine and 10 mg of intracoronary papaverine (48 +/- 25, 52 +/- 19 and 54 +/- 21 cm/s, respectively; all p less than 0.05 vs. baseline) and was significantly higher than in group 2 (37 +/- 24, 32 +/- 16, 41 +/- 23 cm/s; all p less than 0.05 vs. group 1). The coronary vasodilator reserve ratio (calculated as the ratio of hyperemic to basal mean flow velocity) for adenosine and papaverine was 2.94 +/- 1.50 and 2.94 +/- 1.00, respectively, in group 1 and was significantly and similarly reduced in group 2 (2.16 +/- 0.81 and 2.38 +/- 0.78, respectively; both p less than 0.05 vs. group 1). Low dose bolus injection of adenosine increased mean velocity equivalently to that after continuous infusion of 100 micrograms/kg, but less than after papaverine. There was a strong correlation between adenosine infusion and papaverine for both mean coronary flow velocity and coronary vasodilator reserve ratio (r2 = 0.871 and 0.325; SEE = 0.068 and 0.189, respectively; both p less than 0.0005). No patient had significant arrhythmias or prolongation of the corrected QT (QTc) interval with adenosine, but papaverine increased the QT (QTc) interval from 445 +/- 44 to 501 +/- 43 ms (p less than 0.001 vs. both maximal adenosine and baseline) and produced nonsustained ventricular tachycardia in one patient.(ABSTRACT TRUNCATED AT 400 WORDS)

Inability of coronary blood flow reserve measurements to assess the efficacy of coronary angioplasty in the first 24 hours in unselected patients

To determine functional and anatomic changes in the first 24 hours after coronary angioplasty, we studied at random 15 patients (9 men, mean age 60 years) who underwent coronary angioplasty of 16 coronary arteries. Quantitative coronary angiography and coronary flow reserve measurements from digitized coronary angiograms were performed before, immediately after, and 24 hours after coronary angioplasty. Calculated were the minimal luminal diameter, obstruction area, and percentage diameter stenosis from two preferably orthogonal projections. Prior myocardial infarction in the myocardial region of interest was present in four patients. Seven patients had multivessel disease. Collateral vessels supplying the compromised flow region were observed in three patients. Six patients had refractory unstable angina pectoris. After coronary angioplasty, angiographically visible dissection was noted in six patients, whereas side branch occlusion was observed in one. Minimal luminal diameter before, immediately after, and 24 hours after was 0.93 +/- 0.18 mm, 1.53 +/- 28 mm, and 1.53 +/- 0.21 mm, respectively; obstruction area was 0.70 +/- 0.26 mm2, 1.92 +/- 0.69 mm2, and 1.87 +/- 0.51 mm2, respectively; diameter stenosis was 60.4 +/- 8.0%, 36.8 +/- 11.4%, and 37.6 +/- 5.3%, respectively. The coronary flow reserve (lower limit of normal with this technique 3.4) was essentially the same before and immediately after coronary angioplasty (1.26 +/- 0.59 vs 1.30 +/- 0.42, p = NS) with a slight improvement to 1.78 +/- 0.90 (p less than 0.05) 1 day later. Coronary artery dimensions correlated poorly with coronary blood flow reserve before and after angioplasty.(ABSTRACT TRUNCATED AT 250 WORDS)

Percutaneous coronary rotational angioplasty: preliminary clinical and quantitative imaging results

To determine anatomical and functional changes within the first 24 hours after percutaneous coronary rotational angioplasty (PCRA-ROTABLATOR, Biophysics International, USA), we studied 5 patients (4 men) with a mean age of 55 years (range 52-59) using quantitative coronary angiography, coronary flow reserve from digitized coronary angiograms, quantitative left ventricular angiography, and 99mTechnetium-MIBI SPECT imaging before PCRA, immediately after, and 24 hours after. The minimal luminal diameter and obstruction area showed a moderate increase immediately after PCRA, with a substantial further improvement after 24 hours. The mean coronary flow reserve before PCRA and 24 hours after (1.65 +/- 0.31 vs. 1.81 +/- 0.37; p = NS) remained unchanged. Although the global ejection fraction showed slight impairment immediately after PCRA, this was restored 24 hours later. Only the contribution to regional ejection fraction in the regions supplied by the treated coronary artery attributed to the decrease of global ejection fraction. Before and after PCRA, Tc-99m MIBI tomography performed at rest revealed no perfusion defects in the myocardial regions related to the coronary arteries undergoing the intervention.

A simplified method to measure coronary blood flow velocity in patients: validation and application of a Judkins-style Doppler-tipped angiographic catheter

To facilitate more rapid and safe measurement of coronary flow velocity reserve in patients, we developed a Judkins-style angiographic catheter tipped with a 20 MHz Doppler crystal. In 19 patients without coronary artery disease, resting and hyperemic (10 mg intracoronary papaverine) mean and phasic coronary flow velocity signals were measured with the Judkins-style and 2.5F intracoronary Doppler catheters at identical coronary loci. Mean coronary flow velocity at rest was similar (14 +/- 8, 10 +/- 7 cm/sec, p = ns), but was higher during hyperemia for the Judkins-Doppler (41 +/- 8 versus 32 +/- 14 cm/sec, p less than 0.05). Coronary flow velocity reserve, calculated as the ratio of mean velocity at rest to mean velocity following papaverine, was 3.3 +/- 1.4 and 3.7 +/- 1.2 units (p = ns) for the Judkins and intracoronary Doppler techniques, respectively (r = 0.801, p less than 0.001). The Judkins-style Doppler catheter technique permits flow velocity and coronary flow velocity reserve measurements that correlate strongly with those of the intracoronary catheter technique, facilitating safe, quick, and accurate assessment of coronary physiology.

Effect of abruptly increased intrathoracic pressure on coronary blood flow velocity in patients

To assess the effects of abruptly increased intrathoracic pressure on coronary blood flow, arterial pressure, heart rate, and intracoronary Doppler blood flow velocity were measured continuously during cough(s) and again during the four phases of the Valsalva maneuver in 14 patients. Coughing significantly increased the systolic pressure (137 +/- 25 to 176 +/- 30 mm Hg), diastolic pressure (72 +/- 10 to 84 +/- 18 mm Hg), and arterial pulse pressure (65 +/- 27 to 92 +/- 35 mm Hg), with no change in heart rate. The mean coronary flow velocity decreased (17 +/- 10 to 14 +/- 12 cm/sec, p less than 0.03). During the Valsalva maneuver, despite marked reduction in the mean arterial pressure during phase III (96 +/- 12 to 68 +/- 14 mm Hg, p less than 0.05), the reduction of coronary blood flow velocity did not achieve statistical significance. These data demonstrate that neither type of abrupt physiologic increase in intrathoracic pressure enhances coronary blood flow. Coughing does not improve coronary perfusion pressures or flow velocity, despite marked increases in arterial diastolic pressure. The Valsalva maneuver, for the most part, does not significantly alter coronary blood flow velocity.

Ventricular arrhythmia due to intracoronary papaverine: analysis of QT intervals and coronary vasodilatory reserve

Intracoronary papaverine commonly produces striking QT interval prolongation with rare but serious ventricular dysrhythmias reported. Because of 3 cases of severe papaverine-induced dysrhythmia in our laboratory, QT intervals and hemodynamic and intracoronary velocity data collected during intracoronary papaverine administration were retrospectively reviewed in 34 patients; 20 patients with angiographically normal coronary arteries (group 1) and 14 patients (group 2) before and (group 2) after single-vessel left coronary angioplasty. QT intervals increased from 394 +/- 44 to 464 +/- 73 msec, 414 +/- 47 to 504 +/- 95 msec, and 410 +/- 41 to 486 +/- 75 msec for groups 1 and 2 before and after angioplasty, respectively (all P less than 0.01). There was no correlation with hemodynamic, electrocardiographic, or coronary vasodilatory reserve responses and change in QTc interval. In the 3 index patients having significant papaverine-related arrhythmias, a baseline QT interval was prolonged (after prior papaverine exposure) in only 1 in association with torsade de pointes. These data indicate that QT interval prolongation after papaverine is a common occurrence, but that the production of ventricular dysrhythmia is probably idiosynchratic in origin. In view of these findings, we recommend that appropriate antiarrhythmic preparations be in place for patients receiving intracoronary papaverine.