1. Introduction
The effect of percutaneous coronary intervention (PCI) on coronary microvascular
function and the prognostic implication of pre and post-procedural index of
microvascular resistance (IMR) has been shown in previous studies [1, 2, 3]. Coronary
rotational atherectomy (RA) is an efficient way to facilitate balloon or stent
delivery and optimize stent expansion by physical removal of hard plaque via
lumen enlargement [4, 5]. Current PCI guidelines state that RA is a reasonable
approach for the treatment of heavily calcified plaques that cannot be crossed by
a balloon catheter or adequately dilated before stent implantation [6]. However,
the RA procedure has previously been reported to be associated with microvascular
disorder resulting from microcirculatory obstruction [5].
The pressure-temperature wire-derived coronary flow reserve (CFR) and IMR have
constituted the reference standard to assess the status of coronary
microcirculation thus far [7, 8]. Prior studies have indicated that there are
major limitations to the pressure wire-derived CFR calculation; the maximal
hyperemic coronary blood flow is strongly pressure-dependent, and the pressure
wire-derived method appears to systematically underestimate the CFR values [9].
However, the pressure-temperature wire-derived IMR shows good specificity and
reproducibility compared with CFR [10, 11], whereas the invasive measurement
increases additional intracoronary performance and prolongs the operation time.
Thus, to a certain degree, the invasive measurement raises unpredictable
procedural risks, especially when faced with treating complicated lesions or in
urgent situations. Alternatively, multiple pressure-wire-free tools, such as
angiography-derived index of microcirculatory resistance, to assess coronary
microvascular dysfunction have been developed [12]. The pressure-wire-free method
was revealed to be well correlated with wire-derived IMR for estimation of
microcirculatory function [13]. A novel coronary angiography-derived index of
microvascular resistance (caIMR) shows good agreement with pressure-temperature
wire-based IMR and has similar accuracy; thus, it has been proposed as a
well-adopted non-invasive physiological assessment of coronary microcirculation
function [14, 15, 16]. The effect of RA on coronary microcirculation function remains
unclear, and this study aimed to investigate coronary microcirculatory function
indicated by caIMR in patients undergoing RA.
2. Materials and Methods
2.1 Study Population
Between January 2013 and December 2021, consecutive RA procedures in patients
with severe coronary artery calcification lesions and significant stenosis
(stenosis 75% of the vessel diameter) from a dedicated RA database were
retrospectively analyzed. Severe coronary artery calcification was defined
visually with fluoroscopy as the presence of radio-opacities within the vessel
wall without cardiac motion before contrast injection or determined by the
presence of 270° of high-intensity echoes with acoustic
shadowing at one cross-section on intravascular ultrasound (IVUS) [17, 18].
Patients who underwent chronic total occlusion PCI and patients with acute
coronary syndrome (ACS) who underwent primary PCI or urgent invasive PCI were
excluded. Considering the requirements of high-quality coronary angiographic
images, RA procedures containing unclear contrast opacification, marked vascular
overlap or distortion of the targeted vessel, or poor-quality angiographic images
which were difficult to analyze were excluded from the study. All patients were
treated with 100–300 mg aspirin and a loading dose of 300 mg of clopidogrel
before the procedure. Dual antiplatelet therapy was continued for at least 12
months, followed by mono antiplatelet therapy with aspirin (100 mg/day) or
clopidogrel (75 mg/day) indefinitely. The study was approved by the institutional
ethics committee, and all patients provided written informed consent to undergo
coronary angiography and the intervention procedure. Since caIMR data were
collected retrospectively, informed consent for the use of caIMR was waived
according to the institutional ethics regulations with regard to the
observational nature of this study.
2.2 RA Procedure
Coronary RA was performed using a Rotablator Rotational Atherectomy System
(Boston Scientific, Marlborough, MA, USA). Standard techniques for PCI were
performed by an experienced operator. The most widely adopted institutional
protocol for rotablation was used. The preferred burr-to-artery ratio was 0.5,
and a smaller (1.25-mm) burr was initially used more often, followed by a larger
(1.50-mm, 1.75-mm) burr. Before approaching the target lesion, the burr advanced
at a low speed of 60,000 to 70,000 revolutions per minute (rpm). The working
rotational speed of the burr ranged from 130,000 to 180,000 rpm. When the target
lesion could not be fully dilated, a higher-speed (180,000 rpm)
atherectomy was performed. Each pass was limited to 30 seconds. During
the RA procedure, patients received unfractionated heparin with an initial bolus
of 80–100 U/kg and additional boluses of 1000 U/h. A Rota-flush solution
contains 12,500 units of unfractionated heparin, 5 mg of verapamil, and 5 mg of
nitroglycerin in a 1-L bag of saline solution.
The RA was performed when the target lesion was deemed undilatable by a balloon
based on angiography and/or IVUS findings indicated the requirement of planned
RA. RA procedures performed when it was not possible to fully expand the target
lesion were regarded as rescue RA. The use of IVUS for the evaluation of lesion
features and stent expansion was left to the discretion of the operator. After
RA, patients received pre-dilation with conventional, scoring, or cutting
balloons, as determined by the operator. When adequate pre-treatment results were
achieved, one or more drug-eluting stents were implanted.
2.3 Peri-Procedural Adverse Events
We established a dedicated RA database to record demographic, angiographic, and
procedural data, including characteristics of RA and peri-procedural events, as
well as hospitalization information. Peri-procedural adverse events (PPAEs)
including coronary slow flow or no flow post-RA, coronary dissection, burr
entrapment, side branch occlusion, peripheral vascular complications,
contrast-induced nephropathy, procedure-related myocardial infarction (MI), and
in-hospital death were recorded. Coronary slow flow/no flow refers to instant
thrombolysis in myocardial infarction (TIMI) flow grade 3 after the RA
procedure without visible thrombosis, dissection, or spasm. Procedure-related MI
was defined as elevation of cardiac troponin (cTn) 5 times the upper limit of
normal and recurrent symptoms with or without new ST-segment changes. An increase
of cTn values in patients with normal baseline values or a rise of cTn values
20% of the baseline were regarded as myocardial injury [19]. The primary
outcome was a composite of post-RA TIMI flow grade 3 in the target vessel,
myocardial injury, procedure-related MI, and cardiac death during
hospitalization.
2.4 caIMR Measurement
A three-dimensional mesh of the target artery was reconstructed based on two
coronary angiographic projections which were at least 30° apart and had
no vessel overlap. In theory, the caIMR (unit: mmHgs/mm) was computed as
follows:
(1)
In the above equation, Pd is the mean distal coronary pressure at the
maximal hyperemia. The hyperemic Pd was calculated via the Navier-Stokes
equation. A specially designed computational fluid dynamics model for the
steady-state laminar flow has been previously described in detail [20]. This
method was used to compute the pressure drop (P) along meshed
coronary arteries from the inlet to the distal coronary artery (Pd [unit:
mmHg] = Pa–P). Pa represents the maximal
hyperemic mean aortic pressure, which was computed by averaging the pressure
waves in three cardiac cycles. Pa is calculated using a mathematical
formula expatiated in previous studies [14, 20]. L is a non-dimensional constant
that simulates the length measured from the inlet to the distal artery, and it is
generally 75 representing a 75-mm distance downstream from the coronary inlet.
V (unit: mm/s) is the mean blood flow velocity at diastole, and it
is indicative of the contrast passing length (mm)/diastolic time interval (s).
The contrast passing length can be calculated as the distance moved by the
contrast medium in three-dimensional reconstructed coronary arteries during the
diastolic period. K is a constant (K = 2.1), and KV is
assumed to be the maximal hyperemic flow velocity [21, 22]. The caIMR computation
was performed using a FlashAngio system (Rainmed Ltd, Suzhou, China), and the
measurements were performed by blinded operators. In the target vessels, caIMR
was calculated at the stage of before PCI and after finalizing PCI. In reference
vessels, caIMR was obtained at the stage of before PCI. Considering the potential
impact of wedge pressure resulted from collateral flow on caIMR under the
circumstance of severe stenosis being present, a corrected caIMR following Yong’s
formula was calculated in all patients [23].
2.5 Statistical Analysis
Continuous variables are expressed as the mean standard deviation or
median (interquartile range), as appropriate. Categorical variables are presented
as numbers and percentages. The chi-square test or Fisher’s exact test was used
for the comparison of categorical variables. The Student’s t test or
Mann-Whitney rank-sum test was used to test differences among continuous
variables based on their distributions. A multivariable analysis using a logistic
regression model was conducted to determine predictors of the primary outcome,
and the results are expressed as odds ratios (ORs) with 95% confidence intervals
(CIs). Variables suggested to be related to the outcome of interest according to
clinical consideration and with p 0.05 in the univariate analysis
were adopted as candidate predictors for the multivariate analysis. Two-tailed
p 0.05 was considered statistically significant for all tests. All
statistical analyses were performed using SPSS version 20.0 (IBM Corporation,
Armonk, NY, USA).
3. Results
3.1 Baseline, Angiographic, and Procedural Characteristics
A total of 192 consecutive patients who underwent RA between January 2013 and
December 2021 were enrolled in this study. Thiry-seven patients with coronary
angiography involving unclear contrast opacification, marked vascular overlap or
distortion of the targeted vessel, poor-quality angiographic images, or lack of
two images that were 30° apart were excluded. In the final
analysis, 155 RA procedures were included. Detailed clinical baseline,
angiographic and procedural characteristics are shown in Table 1. All patients
had a normal TIMI flow grade before the RA procedure. The left anterior
descending artery (LAD) accounted for most cases of treated arteries (127,
81.9%). The percentage of post-RA myocardial injury was 23.9% (n = 37). Most
PPAEs were minor and without unfavorable prognoses. The common PPAEs were
procedure-related MI (17, 11%) and post-RA TIMI flow grade 3 (13, 8.4%). The
occurrence of TIMI flow 3 was more often observed in LAD (10/13, 76.9%). Burr
entrapment occurred in two (1.3%) patients and was successfully relieved by
repeat balloon dilation following removal of the whole RA system. One (0.6%)
patient with a left ventricular ejection fraction of 20% died due to refractory
heart failure during hospitalization. No cardiac tamponade occurred, and no
definite or probable stent thrombosis was recorded in any of the patients.
Table 1.Clinical baseline, angiographic and procedural characteristics
for the study population.
Variables |
n = 155 |
Clinical baseline characteristics |
|
Age (years) |
70.1 9.1 |
Male gender |
94 (60.6) |
Hypertension |
118 (76.7) |
Diabetes mellitus |
76 (49.0) |
Current smoker |
52 (33.5) |
Previous MI |
22 (14.2) |
Prior PCI |
72 (46.5) |
UAP |
87 (56.1) |
eGFR (mL·min·1.73) |
73.8 23.6 |
LVEF |
61.1 9.2 |
Angiographic and procedural characteristics |
|
PCI access |
|
|
Transradial |
126 (81.3) |
|
Transfemoral |
29 (18.7) |
Three-vessel coronary disease |
112 (72.2) |
Contrast volume (mL) |
266.5 86.5 |
Target vessel |
|
|
LAD |
127 (81.9) |
|
LCX |
7 (4.5) |
|
RCA |
21 (13.5) |
20 mm lesion |
128 (82.6) |
Bifurcation lesion |
84 (54.2) |
Planned RA |
109 (70.3) |
Rescue RA |
46 (29.7) |
IVUS use |
73 (47.1) |
Number of rotational times |
4 (3, 5) |
Maximum RA time of each pass (seconds) |
17.0 3.9 |
Maximum rotational speed (10,000 rpm) |
15.8 1.3 |
Number and size of burrs |
|
|
1 |
138 (89) |
|
2 |
17 (11) |
|
1.25 mm |
103 (59.9) |
|
1.50 mm |
68 (39.5) |
|
1.75 mm |
1 (0.6) |
Number of stents |
2 (2, 2) |
Myocardial injury |
37 (23.9) |
Peri-procedural adverse events |
33 (21.3) |
Instant TIMI flow grade 3 |
13 (8.4) |
No flow |
1 (0.6) |
Procedure related-MI |
17 (11) |
In-hospital death |
1 (0.6) |
The primary outcome |
61 (39.3) |
Values are mean standard deviation, median (interquartile range) or n
(%). MI, myocardial infarction; PCI, percutaneous coronary intervention; UAP,
unstable angina pectoris; eGFR, estimated glomerular filtration rate; LVEF, left
ventricular ejection fraction; LAD, left anterior descending artery; LCX, left
circumflex; RCA, right coronary artery; RA, rotational atherectomy; IVUS, intravas-
cular ultrasound; rpm, revolutions per minute; TIMI, thrombolysis in myocardial infarction.
The primary outcome was a composite of TIMI flow 3 post-RA in the target
vessel, myocardial injury, procedure related MI, and cardiac death during
hospitalization. |
3.2 caIMR, Myocardial Injury, and Procedure-Related MI
There were no significant differences in pre-RA caIMR measurements between the
target and reference vessels (15.2 5.2 vs. 14.6 7.5, p =
0.466). However, post-RA caIMRs were significantly higher than pre-RA caIMRs in
the target vessels (16.0 7.0 vs. 14.5 7.5, p = 0.029),
as shown in Fig. 1. Patients with post-RA caIMR 25 accounted for nearly
12% (n = 16) of those with pre-RA caIMR 25. Among patients with pre-RA caIMR
25, the incidence of myocardial injury was significantly lower in those with
post-RA caIMR 25 than that in those with post-RA caIMR 25 [25 (20.5%)
vs. 8 (50.0%), p = 0.022]. Furthermore, the rates of procedure-related
MI were comparable between the two groups [12 (9.8%) vs. 2 (12.5%), p
= 0.747], as shown in Fig. 2.
Fig. 1.
A paired comparison of caIMR in the target and reference
vessels. (A) A paired comparison of pre-RA caIMR between the target and
reference vessels. (B) A paired comparison of pre-RA and post-RA caIMR in the
target vessels. MI, myocardial infarction; caIMR, coronary angiography-derived
index of microvascular resistance; RA, rotational atherectomy.
Fig. 2.
Occurrences of myocardial injury and procedure-related MI among
patients with pre-RA caIMR 25. MI, myocardial infarction; caIMR, coronary
angiography-derived index of microvascular resistance; RA, rotational
atherectomy.
3.3 caIMR, Myocardial Injury, and Procedure-Related MI Stratified by
Post-RA TIMI Flow
Patients with post-RA TIMI flow grade 3 had a significantly higher pre-RA
caIMR (23.5 10.2 vs. 13.7 6.6, p = 0.005), and the
proportion of patients with pre-RA caIMR 25 in the group with post-RA
TIMI flow grade 3 was greater (61.5% vs. 6.3%, p 0.001) than
that in the group with post-RA TIMI flow grade of 3. Similarly, patients with
post-RA TIMI flow grade 3 had post-RA higher caIMR (25.6 8.0 vs. 15.1
6.2, p 0.001), and the proportion of patients with post-RA
caIMR 25 in the group with post-RA TIMI flow grade 3 was greater
(53.8% vs. 7.0%, p 0.001). There was no significant difference
between the group with post-RA TIMI flow grade 3 and that with TIMI flow grade
of 3 concerning the rate of myocardial injury (38.5% vs. 22.5%, p =
0.342). More patients had procedure-related MI in the group with post-RA TIMI
flow grade 3 than those in the group with TIMI flow grade of 3 (30.8% vs.
9.2%, p = 0.040), as summarized in Table 2.
Table 2.caIMR, myocardial injury and procedure-related MI according to
post-RA TIMI flow.
Variables |
post-RA TIMI flow grade 3 |
post-RA TIMI flow grade 3 |
p value |
|
(n = 13) |
(n = 142) |
|
pre-RA caIMR |
23.5 10.2 |
13.7 6.6 |
0.005 |
|
25 |
8 (61.5) |
9 (6.3) |
0.001 |
|
25 |
5 (38.5) |
133 (93.7) |
|
post-RA caIMR |
25.6 8.0 |
15.1 6.2 |
0.001 |
|
25 |
7 (53.8) |
10 (7.0) |
0.001 |
|
25 |
6 (46.2) |
132 (93.0) |
|
Myocardial injury |
5 (38.5) |
32 (22.5) |
0.342 |
Procedure-related MI |
4 (30.8) |
13 (9.2) |
0.040 |
Values are mean standard deviation or n (%). caIMR, coronary
angiography-derived index of microvascular resistance; MI, myocardial infarction;
TIMI, thrombolysis in myocardial infarction; RA, rotational atherectomy. |
3.4 Predictors of Primary Outcome in Patients who Underwent RA
Candidate predictors in the univariate analysis included age, hypertension,
diabetes mellitus, previous MI, estimated glomerular filtration rate, number of
diseased vessels, lesions 20 mm, bifurcation lesion, RA strategy (planned
or rescue RA), number of rotational times, maximum RA time of each pass, maximum
rotational speed, pre-RA caIMR, post-RA caIMR, and percentage of pre-RA caIMR
25 and post-RA caIMR 25 in the treated vessels. The variables
entered into the logistic regression model were maximum RA time of each pass and
percentage of pre-RA caIMR 25 and post-RA caIMR 25. Table 3 shows
multivariate predictors of the primary outcome in patients who underwent RA. The
multivariable analysis revealed that the independent predictors of the primary
outcome were maximum RA time of each pass (OR: 1.127, 95% CI: 1.025–1.239,
p = 0.014) and caIMR pre-RA 25 (OR: 3.254, 95% CI:
1.054–10.048, p = 0.040) for patients who underwent RA.
Table 3.Predictors of the primary outcome in patients who underwent
RA.
Variable |
Univariate OR (95% CI) |
p value |
Adjusted OR (95% CI) |
p value |
Age (years) |
1.034 (0.997–1.073) |
0.075 |
|
|
Hypertension |
1.420 (0.649–3.110) |
0.380 |
|
|
Diabetes mellitus |
0.989 (0.518–1.886) |
0.973 |
|
|
Previous MI |
1.028 (0.991–1.066) |
0.136 |
|
|
eGFR (mL·min·1.73) |
0.990 (0.976–1.004) |
0.165 |
|
|
number of diseased vessels |
1.017 (0.985–1.049) |
0.305 |
|
|
lesions 20 mm |
1.368 (0.571–3.281) |
0.482 |
|
|
bifurcation lesion |
0.994 (0.520–1.897) |
0.985 |
|
|
RA strategy (planned or rescue RA) |
1.449 (0.720–2.914) |
0.298 |
|
|
number of rotational times |
1.127 (0.999–1.271) |
0.053 |
|
|
maximum RA time of each pass (seconds) |
1.121 (1.021–1.230) |
0.016 |
1.127 (1.025–1.239) |
0.014 |
maximum rotational speed |
1.000 (1.001–1.100) |
0.705 |
|
|
pre-RA caIMR |
1.027 (0.984–1.073) |
0.219 |
|
|
pre-RA caIMR 25 |
3.227 (1.125–9.253) |
0.029 |
3.254 (1.054–10.048) |
0.040 |
post-RA caIMR |
1.018 (0.973–1.066) |
0.441 |
|
|
post-RA caIMR 25 |
3.592 (1.269–10.166) |
0.016 |
2.834 (0.958–8.386) |
0.060 |
RA, rotational atherectomy; OR, odds ratio; CI, confidence interval; MI,
myocardial infarction; eGFR, estimated glomerular filtration rate; caIMR,
coronary angiography-derived index of microvascular resistance. The primary
outcome was a composite of TIMI flow 3 post-RA in the target vessel,
myocardial injury, procedure-related MI, and cardiac death during
hospitalization. |
4. Discussion
The aim of this study was to evaluate coronary microcirculation function
indicated by caIMR in patients undergoing RA. Our main findings are as follows:
(1) Post-RA caIMR, which indicates coronary microcirculation function, was
greater than pre-RA caIMR in the treated vessels. Patients with 25
post-RA caIMR accounted for nearly 12% of those with pre-RA caIMR 25; (2)
among patients without increased pre-RA caIMR, those with post-RA caIMR
25 were associated with a significantly increased incidence of myocardial
injury compared to those with post-RA caIMR 25; (3) patients with post-RA TIMI
flow grade 3 showed significant differences in both pre- and post-RA caIMR
compared with those of patients with normal TIMI flow; (4) among patients who
underwent RA, those receiving longer RA time of each pass and with pre-RA caIMR
25 had worse outcomes.
It has been demonstrated that RA facilitates procedural success in treating
calcified plaques, especially in complex ostial lesions and bifurcation lesions,
which feature bulky plaque and unfavorable geometry for stent deployment [24, 25]. While there have always been concerns regarding microcirculatory dysfunction
associated with RA, analyzing the CFR and coronary microvascular resistance using
intracoronary Doppler guidewire has been considered to be the most reliable
method for coronary microcirculation assessment [26, 27]. However, intracoronary
Doppler guidewire is unavailable in current practice. The pressure-temperature
wire-derived CFR is associated with variations in measurement and has unsatisfied
reproducibility [9, 28]. The pressure-temperature wire-derived measurements of
coronary microcirculation, indicated by IMR, seem impracticable with regard to
real-world applicability, particularly when applied in urgent situations or
complex PCI. Previous studies have demonstrated that caIMR is a feasible
alternative for the evaluation of coronary microcirculatory function [14, 15, 16].
In the present study, post-RA caIMRs were significantly higher than pre-RA
caIMRs in the treated vessels. Nearly 1/8th of patients without demonstrated
microcirculatory dysfunction indicated by pre-RA caIMR 25 had an increased
post-RA caIMR (25). To our knowledge, this is the first report on the
evaluation of microcirculation function indicated by pre-RA caIMR in patients
undergoing RA. It has been revealed that the RA debris containing atheromatous
particles and platelet-rich tissue might be apt to induce embolic formation,
subsequently resulting in clogging within the distal coronary microcirculation
[29, 30]. We presumed that the resultant elevation of post-RA caIMR was mainly
attributable to the microvascular embolization of atherosclerotic debris and
associated thrombi [5]. Further, the possibility of microvascular spasm induced
by RA cannot be excluded, even though nitroglycerin was continuously administered
during the procedures.
In our study, we observed that among patients without microcirculation
dysfunction reflected by pre-RA caIMR 25, the incidence of myocardial injury
was significantly higher in those with post-RA caIMR 25 than in those
with post-RA caIMR 25, while the rates of MI were comparable. This implies
increased microvascular resistance resulting from micro-embolization of the
debris generated during debulking of the lesion might cause detrimental effects
such as myocardial injury. Most particles created by the RA procedure are 10
m and have a mean diameter of 5 m. They are smaller
than normal, mature erythrocytes and can traverse coronary microvasculature
cleared by the reticuloendothelial system [31]. However, in certain
circumstances, the microdebris might be either too large to penetrate through the
distal microcirculation or too abundant to be readily absorbed, and is
consequently followed by increased caIMR, which indicates distal microvascular
dysfunction [32]. However, procedure-related MI alone cannot adequately explain
the difference observed between those with and without increased post-RA caIMR in
our study, and more factors might be involved during the RA procedure. For
instance, the release of adenosine from the ischemic myocardium due to the
aggregation of the ablated microdebris could have made the RA procedure even more
complicated.
Slow flow or no flow is not a rare phenomenon during RA, with reported rates
varying from 7–10% [32, 33]. The incidence of instant TIMI flow grade 3 in
the present study was 8.4%, and no flow occurred only in one case. Slow flow may
lead to hemodynamic instability due to serious hypoperfusion, which is thought to
be related to reduced coronary artery conductance [33, 34], which in turn is
associated with increased occurrence of MI, rather than myocardial injury, as
shown in our study. In our study, a reduction in coronary conductance was
indicated by the finding that more patients with TIMI flow grade 3 had higher
post-RA caIMR. RA did not definitely have a detrimental effect on the
microcirculatory status in patients with post-RA TIMI flow grade 3, however, the
observation that more patients with post-RA TIMI flow grade 3 had higher
pre-RA caIMR indicates that the embolization of ablated microdebris and
associated microthrombi subsequently followed by slow flow more likely occurred
in patients with baseline coronary microcirculatory dysfunction.
In our adjusted analysis for various related variables, patients with maximum RA
time of each pass had a significantly increased risk of the primary outcome.
Prolonged rotational duration does not necessarily confer beneficial effects,
which is consistent with a prior report which found that adopting an aggressive
RA strategy did not offer advantage, and was sometimes even detrimental [35].
Notably, our study revealed that pre-RA caIMR 25 in the treated vessels,
but not post-RA caIMR 25, was identified to be an independent predictor
of the primary outcome with approximately a 3-fold increase in risk of the
primary outcome among patients undergoing RA. The underlying coronary
microcirculatory dysfunction indicated by an elevation of pre-RA caIMR was
associated with a benign outcome in patients who underwent RA, and increased
post-RA caIMR might only suggested to be a resultant slow flow.
5. Limitations
This study has several limitations. First, this was a single-center
retrospective observational study, and the lack of a control group weakened the
strength of the study’s implications. However, we performed a self-control
analysis and measured caIMR in the reference vessels. Second, the decision to
perform RA was at the discretion of the interventionist, and there was sustained
improvement in the RA techniques across the cases. Thus, the results of our study
should be interpreted with caution. Third, as the caIMR measurement was related
to Pd and V, as mentioned above in the methods section,
severe stenosis in the target vessels might influence the pressure and velocity
in the distal vessel to some degree. Nevertheless, it has been reported that
minimal microvascular resistance does not change with epicardial stenosis
severity, and IMR is a specific index of microvascular resistance when coronary
wedge pressure was taken into account [10, 36]. Despite the value of caIMR in our
study was a corrected IMR following Yong formula, whether wire-derived IMR could
be translated to caIMR deserve further study. Fourth, in this study, we only
observed the instant and short-term impact of RA on coronary microcirculation,
and long-term angiography follow-up data were not obtained. Analyzing the
peri-procedural and in-hospital outcomes combined with long-term outcomes of RA
affecting coronary microcirculation should be considered in future studies.
6. Conclusions
There were significant changes in the coronary microcirculation function of the
target vessel after receiving RA, as indicated by a increase in post-RA caIMR
compared with pre-RA caIMR. Post-RA TIMI flow grade 3 was more likely to be
observed in patients with baseline coronary microcirculatory dysfunction.
Patients receiving longer RA time of each pass and with pre-RA caIMR 25
had worse outcomes. In the future, further investigation of the impact of RA on
long-term coronary microcirculatory function is warranted. To justify the
clinical performance of caIMR, prospective and mode in-depth analysis should be
designed also for short-term outcomes.
Abbreviations
RA, rotational atherectomy; caIMR, coronary angiography-derived index of
microvascular resistance; PCI, percutaneous coronary intervention; CFR, coronary
flow reserve; CMR, coronary microvascular resistance; IMR, index of microvascular
resistance; ACS, acute coronary syndrome; PPAE, peri-procedural adverse event;
MI, myocardial infarction; rpm, revolutions per minute; TIMI, thrombolysis in
myocardial infarction; cTn, cardiac troponin; CFD, computational fluid dynamics;
MAP, mean aortic pressure.
Author Contributions
Study conception and design—H-PZ, HA. Acquisition of data—H-PZ, XP, LL,
G-DT, YZ, G-JY, N-XZ, F-CS. Analysis and interpretation of data (e.g.,
statistical analysis, computational analysis)—HL, XP, H-PZ, HA. Writing,
review, and/or revision of the manuscript—HL, XP, Y-DF, H-PZ. Study
supervision—H-PZ. All authors contributed to editorial changes in the
manuscript. All authors read and approved the final manuscript.
Ethics Approval and Consent to Participate
The study was approved by the institutional Ethics Committee (Approval No.
2019BJYYEC-021-02), all patients signed informed consent to undergo coronary
angiography and the intervention procedure. Because data on caIMR were collected
retrospectively, informed consent on the use of caIMR was waived given the
institutional ethics regulations with regard to observational study nature.
Acknowledgment
Not applicable.
Funding
The present study was supported by National High Level Hospital Clinical
Research Funding (BJ-2018-201), Chinese Academy of Medical Sciences Innovation
Fund for Medical Sciences (Grant Number 2021-I2M-C&T-A-019), and Beijing
Municipal Science & Technology Commission, Administrative Commission of
Zhongguancun Science Park (Grant Number Z211100002921008).
Conflict of Interest
The authors declare no conflict of interest.
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