Demographics and prevalence of cardiovascular risks
The study population comprised of 146 males (39%) and 228 females (61%). The ages ranged from 17 to 90 years with a mean of 56 ± 14 years. In this study, 32% (n = 118) of the population was more than 65 years old, 39% (n = 39) were male, 5% (n = 20) were active smokers or ex-smokers, 11% (n = 42) had family history of IHD, 27% (n = 99) had diabetes, 46% (n = 171) had hypertension, 33% (n = 124) had dyslipidaemia, 5% (n = 18) had kidney disease, 3% (n = 12) had stroke, and 5% (n = 20) had pre-existing heart disease (i.e., valve-related disease and congenital heart disease). There were 63% (n = 235) found to have at least one (1) cardiovascular risk factor, and they were categorised in the CVR (Presence) group. The remaining 37% (n = 139) of the study population, who had no CVR at all were categorised in the CVR (Absence) group (Fig. 1).
Ramus Intermedius And Its Role In Plaque Deposition
From the CCTA findings, 68% (n = 253) of the study population had LMBA bifurcation (i.e., absence of RI vessel), 28% (n = 106) of the study population had a single RI vessel forming a trifurcation, and 4% (n = 15) of the study population had double RI vessels which therefore forming a quadrifurcation (Fig. 6). In total there were 32% (n = 121) of the study population were noted to have RI. Although the RI can be seen using volume rendering techniques, but it is best seen in the best diastolic contrast phase in axial MPR images (Fig. 6 (b and c)). This study found that the RI itself is at risk for plaque deposition at the LBR (Fig. 7). Of the 121 patients with RI, 12% (14) of them had plaque deposition with stenosis (Fig. 7 (c)). Ten of them had obstructive stenosis and the remaining 4 patients had non-obstructive stenosis.
Plaque Deposition At The Left Bifurcation Region And Its Association With Ramus Intermedius
Figure 1 showed the distribution of plaque depositions at the LMCA, pLAD and pLCx in each CVR groups (absence and presence). Among these 3 regions, the pLAD (44%, n = 163) had the highest prevalence of plaque deposition followed by pLCx (24%, n = 91), and LMCA 18% (n = 68). Analysis on the presence of plaques were further investigated in each CVR group among patients with (n = 121, single or double RI vessels) and without RI (n = 253) (Tables 2 and 3).
Table 2
Multivariate analysis between ramus intermedius and atherosclerosis plaque deposition at the left bifurcation region in patients without cardiovascular risk
Location of plaque deposition
|
Total
|
Ramus Intermedius
|
aOR
|
95% CI
|
p-value
|
Absence
|
Presence
|
LMCA
|
(n = 26)
|
|
|
|
|
|
Proximal (a) only
|
1 (1%)
|
1 (1%)
|
0 (0%)
|
0.0
|
0, 0
|
0.0
|
Distal (b) only
|
16 (12%)
|
9 (10%)
|
7 (15%)
|
2.0
|
1.3, 5.5
|
0.244
|
Both (a and b)
|
9 (6%)
|
2 (2%)
|
7 (15%)
|
8.5
|
1.7, 43.0
|
0.010*
|
pLAD
|
(n = 44)
|
|
|
|
|
|
Medial (d) only
|
2 (1%)
|
2 (2%)
|
0 (0%)
|
0.0
|
0, 0
|
0.0
|
Lateral (c) only
|
24 (17%)
|
11 (12%)
|
13 (28%)
|
3.5
|
1.1, 11.3
|
0.036*
|
Both (c and d)
|
18 (14%)
|
7 (8%)
|
11 (23%)
|
4.3
|
2.1, 17.4
|
0.038*
|
pLCx
|
(n = 27)
|
|
|
|
|
|
Medial (f) only
|
2 (1%)
|
1 (1%)
|
1 (2%)
|
0.0
|
0.0, 0.0
|
0.0
|
Lateral (e) only
|
10 (7%)
|
5 (5%)
|
7 (15%)
|
0.8
|
0.2, 4.4
|
0.872
|
Both (f and e)
|
15 (11%)
|
6 (7%)
|
7 (15%)
|
3.7
|
1.2, 11.4
|
0.769
|
Data are presented as n (%) unless stated otherwise,
*Indicates p < 0.05, aOR: Adjusted odds ratio using Binary logistic regression test with no stenosis in each segment as reference),
Cardiovascular risk (Absence) indicates a patient who has no cardiovascular risk),
No stenosis indicates no plaque deposition found in any of the artery walls; Plaque at both indicate plaque deposition found at both medial and lateral walls,
LMCA: Left main coronary artery, pLAD: Proximal left anterior descending artery, pLCx: Proximal left circumflex artery, RI: Ramus intermedius.
|
Table 3
Multivariate analysis between ramus intermedius and atherosclerosis plaque deposition at the left bifurcation region in patients with cardiovascular risk
Location of plaque deposition
|
Total
|
Ramus Intermedius
|
aOR
|
95% CI
|
p-value
|
Absence
|
Presence
|
LMCA
|
(n = 42)
|
|
|
|
|
|
Proximal (a) only
|
0 (0%)
|
0 (0%)
|
0 (0%)
|
0.0
|
0,0
|
0.000
|
Distal (b) only
|
27 (12%)
|
12 (8%)
|
15 (20%)
|
3.3
|
1.5, 7.5
|
0.064
|
Both (a and b)
|
15 (6%)
|
9 (5%)
|
6 (8%)
|
1.8
|
0.6, 5.2
|
0.305
|
pLAD
|
(n = 119)
|
|
|
|
|
|
Medial (d) only
|
5 (2%)
|
3 (2%)
|
2 (3%)
|
2.3
|
0.3, 16.0
|
0.400
|
Lateral (c) only
|
51 (22%)
|
24 (15%)
|
27 (37%)
|
4.1
|
1.8, 9.5
|
0.001*
|
Both (c and d)
|
63 (27%)
|
39 (24%)
|
24 (32%)
|
2.6
|
1.2, 5.5
|
0.014*
|
pLCx
|
(n = 64)
|
|
|
|
|
|
Medial (f) only
|
2 (1%)
|
1 (1%)
|
1 (1%)
|
1.8
|
0.1, 30.0
|
0.697
|
Lateral (e) only
|
18 (8%)
|
7 (4%)
|
11 (15%)
|
1.8
|
0.6, 6.1
|
0.271
|
Both (f and e)
|
44 (18%)
|
26 (16%)
|
18 (24%)
|
1.1
|
0.5, 2.5
|
0.746
|
Data are presented as n (%) unless stated otherwise,
*Indicates p < 0.05, aOR: Adjusted odds ratio using Binary logistic regression test with no stenosis in each segment as reference),
Cardiovascular risk (Presence) indicates patients who have at least one or more cardiovascular risks,
No stenosis indicates no plaque deposition found in any of the artery walls; Plaque indicates plaque deposition found at both medial and lateral walls,
LMCA: Left main coronary artery, pLAD: Proximal left anterior descending artery, pLCx: Proximal left circumflex artery, RI: Ramus intermedius.
|
In the CVR (Absence) group, there were 26 patients who had plaque depositions at the LMCA. Fourteen of them had the aberrant vessel, RI. In addition, another 7 of them demonstrated plaque depositions at both parts of the LMCA. Ramus intermedius is therefore associated with an eight-fold risk for LMCA atherosclerosis compared to those without RI (aOR = 8.5, 95% CI = 1.7, 43.0, p = 0.01, Table 2, LMCA). Figure 7 (a and b) showed plaque depositions and parts of the LMCA that are best seen in axial and coronal views of the MPR images. The current study reported that the presence of RI was not associated with LMCA plaque formation in the CVR (presence) group (Table 3, LMCA). A similar analysis was done in the pLAD.
In the CVR (Absence) group, there were 44 patients with plaque deposition in the pLAD. Thirteen of them were patients with RI who demonstrated plaque deposition at the lateral wall only. Analysis showed that the presence of RI tripled the risk for plaque deposition at the lateral wall of pLAD (aOR = 3.5, 95% CI = 1.1, 11.3, p = 0.036, Table 2, pLAD). Figure 7 (c) showed plaque deposition at the lateral wall of pLAD which was close to pLAD ostium. Another 11 of them were patients with RI who had plaque deposition at both walls (i.e., the lateral and medial) of pLAD. The presence of RI increases the risk for plaque deposition involving both pLAD walls by four-fold (aOR = 3.5, 95% CI = 1.1, 11.3, p = 0.036, Table 2, pLAD). A similar finding was also found among patients with pre-existing CVR.
In the CVR (Presence) group, 119 patients demonstrated plaque deposition at the pLAD. Twenty-seven of them were patients with RI who had plaque deposition only at the lateral wall. The presence of RI increased the risk for plaque deposition at the lateral wall of pLAD by four-fold compared to those without RI (aOR = 4.1, 95% CI = 1.8, 9.5, p < 0.001, Table 3, pLAD). Another 24 of them were patients with RI who had plaque deposition involving both walls (i.e., the lateral and medial) of pLAD. The presence of RI doubled the risk for plaque deposition involving both pLAD walls compared to those without RI (aOR = 2.6, 95% CI = 1.2, 5.5, p = 0.014, Table 3, pLAD). The aberrant vessel, RI was a significant risk for plaque deposition at the lateral or both walls of the pLAD in both CVR groups.
Among patients without CVR, there were 27 patients who demonstrated plaque deposition at the pLCx. Fifteen of them were patients with RI who had atheroma formation at the lateral, medial and both walls of the pLCx (Table 2, pLCx). Meanwhile, 64 patients with CVR demonstrated plaque depositions at the pLCx. Thirty of them were also demonstrated to have RI, with their plaque deposition noted at the lateral, medial and both pLCx walls (Table 3, pLCx). Figure 7 (c) showed plaque depositions at the lateral wall of the pLCx, which was located adjacent to the pLCx ostium. However, these associations did not reach statistical in both groups (Tables 2 and 3, pLCx).