**7.4 Left ventricular functional indexes changes pre and post-surgery (MRI parameters)**

Figure 12 shows typical short-axis and long-axis magnetic resonance images of patient preand post-SVR and how to calculate shape, eccentricity and sphericity index. It is noted that the long-axis decreased more dramatically compared with short-axis dimension, thereby producing a more spherical LV. Figure 13 shows typical 3-dimensional modeling of LV from CMR images using LVtools pre and post SVR.

The intraobserver and interobserver data for EDV, ESV and mass for pre- and post-surgery groups are shown in Table 9. Table 10 summarizes the mean LV functional indexes pre and post-SVR. Following SVR, there was a significant decrease in the dimensions of both the long- and short-axes of the LV. However, the long-axis dimension of the LV decreased more than the short-axis dimension, resulting in a more spherical ventricle post-SVR. There was a significantly reduction in end-diastolic volume index (EDVI), end-systolic volume index (ESVI), LV stroke volume index (SVI), LV mass index, and peak normalized wall stress after

All 40 patients were treated with CABG and SVR (endoventricular circular patch plasty). The age of the patients averaged 69 years (range, 52-84 years). Among them, 19 patients had severe mitral regurgitation and received additional MVS. 28 patients had CHF. The baseline

Variables Value Male : female 36:4 Age (years) 69 ± 9 Body surface area (m2) 1.98 ± 0.18 Coronary artery disease 39 (98%) Hypertension 19 (48%) Diabetes mellitus 13 (33%) Tobacco 23 (58%) Congestive heart failure 28 (70%) Peripheral arterial disease 3 (8%) Stroke 2 (5%) Creatinine (mg/dL) 1.17 ± 0.29 Prior cardiac surgery 19 (48%)

 I-II 26 (65%) III-IV 14 (35%)

Table 8. Patients' characteristics and clinical data (n=40). This table is related to our work in

**7.4 Left ventricular functional indexes changes pre and post-surgery (MRI parameters)**  Figure 12 shows typical short-axis and long-axis magnetic resonance images of patient preand post-SVR and how to calculate shape, eccentricity and sphericity index. It is noted that the long-axis decreased more dramatically compared with short-axis dimension, thereby producing a more spherical LV. Figure 13 shows typical 3-dimensional modeling of LV from

The intraobserver and interobserver data for EDV, ESV and mass for pre- and post-surgery groups are shown in Table 9. Table 10 summarizes the mean LV functional indexes pre and post-SVR. Following SVR, there was a significant decrease in the dimensions of both the long- and short-axes of the LV. However, the long-axis dimension of the LV decreased more than the short-axis dimension, resulting in a more spherical ventricle post-SVR. There was a significantly reduction in end-diastolic volume index (EDVI), end-systolic volume index (ESVI), LV stroke volume index (SVI), LV mass index, and peak normalized wall stress after

21 (52%)

19 (48%)

Surgical ventricular restoration + coronary artery bypass

Surgical ventricular restoration + coronary artery bypass

Values are mean ± SD or numbers of patients (percentages).

**7.3 Clinical results** 

patient characteristics are summarized in Table 8.

New York Heart Association class

grafting + mitral valve surgery

CMR images using LVtools pre and post SVR.

Surgery

grafting

Ref [19].

SVR (Table 3). The values of LV EDVI, ESVI, LVEF and the contractility index *dσ\*/dtmax* preand post-SVR are also shown in the scatter plots of Figure 14.

Table 10 provides the sphericity index (SI) values in end-diastole and end-systole and its diastolic-systolic change, as well as the % shortening of the long- and short-axes. During a cardiac cycle, LV shape becomes less spherical in systole (SI smaller) than in diastole (SI closer to '1'). The diastolic-systolic change in SI (SIed-SIes) is significantly augmented by the operation, despite the LV chamber becoming more spherical. The % shortening of long-axis is not significantly altered, but the % shortening of the short-axis is significantly increased by the operation. Despite the seemingly unfavorable spherical LV shape post-SVR, the LV contractile function is significantly improved, as indicated by the increased value of *dσ\*/dtmax*.

The scatter plots of figure 14 graphically illustrate pre- and post-SVR values of ventricular end-diastolic volume, end-systolic volume, LVEF and contractility index *dσ\*/dtmax*. From Tables 9 and 10, we can note a significant reduction in end-diastolic volume (318 ± 63 ml vs. 206 ± 59 ml, p<0.01), end-systolic volume (228 ± 58 ml vs. 133 ± 61 ml, p<0.01), LV mass (204 ± 49 g vs. 187 ± 53 g, p<0.01), and peak normalized wall stress (PNWS) (4.64 ± 0.98 vs. 3.72 ± 0.87, p<0.01). Increased sphericity index SI (0.57 ± 0.094 vs. 0.67 ± 0.13, p<0.01) and increased shape factor (S) (0.44 ± 0.085 vs. 0.54 ± 0.089, p<0.01) during end-systole indicates that the LV became more spherical after SVR.


Table 9. Reproducibility data in patients pre- and post-SVR. This table is related to our work in Ref [19].

The prime effect of SVR may be viewed as: (i) effecting a decrease in myocardial oxygen consumption by reduction of LV peak normalized wall stress, resulting in improved functioning of LV, and (ii) augmentation of value of the contractility index *dσ\*/dtmax* (2.69 ± 0.74 s-1 vs. 3.23 ± 0.73 s-1, p<0.01). This improvement may be attributed to (i) increased maximal flow *dV/dtmax* with reduced LV mass, and (ii) improved regional contraction and contractility of the remote myocardium. The improvement in remote myocardial performance is likely due to reduced myocardial stress, along with effective and complete revascularization. This is because the SVR procedure reduces the volume by more dramatically reducing long-axis dimension compared with the short-axis dimension, and producing a more spherical ventricle.

Based on Table 10, increased LV contractile function *d*σ*\*/dtmax* can be not only associated with increased maximal flow *dV/dtmax*, reduced LV mass, and also increased maximal change rate of shape factor *dS/dtmax* (r=0.414, p<0.001). There was also good correlation between *d*σ*\*/dtmax* and LVEF (r=0.69, p<0.001, pre-SVR; r=0.77, p<0.001, post-SVR) (Figure 15).


Table 10. Patients' data pre- and post-SVR. This table is related to our work in Ref [19].

Cardiac Myocardial Disease States (Such as Myocardial Infarction) Cause Left Ventricular Remodeling with Decreased Contractility and Lead to Heart Failure; Interventions by Coronary … 811

810 Biomedical Science, Engineering and Technology

The prime effect of SVR may be viewed as: (i) effecting a decrease in myocardial oxygen consumption by reduction of LV peak normalized wall stress, resulting in improved functioning of LV, and (ii) augmentation of value of the contractility index *dσ\*/dtmax* (2.69 ± 0.74 s-1 vs. 3.23 ± 0.73 s-1, p<0.01). This improvement may be attributed to (i) increased maximal flow *dV/dtmax* with reduced LV mass, and (ii) improved regional contraction and contractility of the remote myocardium. The improvement in remote myocardial performance is likely due to reduced myocardial stress, along with effective and complete revascularization. This is because the SVR procedure reduces the volume by more dramatically reducing long-axis dimension compared with the short-axis dimension, and

increased maximal flow *dV/dtmax*, reduced LV mass, and also increased maximal change rate of

Variables Pre SVR (n=40) Post SVR (n=40) Cardiac index (L/min/m2) 2.84 ± 0.74 2.59 ± 0.74 Mean arterial pressure (mmHg) 85 ± 14 84 ± 8 Systolic blood pressure (mmHg) 115 ± 20 113 ± 10 Diastolic blood pressure (mmHg) 71 ± 12 70 ± 8 End diastolic volume index (ml/m2) 156 ± 39 110 ± 33\* End systolic volume index (ml/ m2) 117 ± 39 77 ± 31\* Stroke volume index (ml/ m2) 39 ± 9 33 ± 8\* Left ventricular ejection fraction (%) 26 ± 7 31 ± 10\* LV mass index (g/m2) 112 ± 25 101 ± 23\* End-diastolic long axis, BAed(cm) 10.89 ± 1.16 8.31 ± 1.00\* End-diastolic short axis, APed(cm) 7.00 ± 0.80 6.64 ± 0.78\* End-systolic long axis, BAes(cm) 10.37 ± 1.20 7.87 ± 1.05\* End-systolic short axis, APes (cm) 5.86 ± 0.98 5.23 ± 1.06\* End-diastolic sphericity Index, SIed 0.65 ± 0.087 0.81 ± 0.11\* End-systolic sphericity index, SIes 0.57 ± 0.094 0.67 ± 0.13\*

Long axis shortening (%) 4.8 ± 3.6 5.4 ± 4.4 Short axis shortening (%) 16.4 ± 6.8 22 ± 9.7\* *dV/dtmax* (ml/s) 364 ± 83 401 ± 81\* Pressure normalized wall stress 4.30 ± 0.95 3.31 ± 0.75\* Stroke work (mmHg·L) 6.61 ± 1.96 5.46 ± 1.64\*

*\*/dtmax* (s-1) 2.69 ± 0.74 3.23 ± 0.73\*

Table 10. Patients' data pre- and post-SVR. This table is related to our work in Ref [19].

shape factor *dS/dtmax* (r=0.414, p<0.001). There was also good correlation between *d*

LVEF (r=0.69, p<0.001, pre-SVR; r=0.77, p<0.001, post-SVR) (Figure 15).

σ

*\*/dtmax* can be not only associated with

0.077 ± 0.043 0.14 ± 0.059\*

σ

*\*/dtmax* and

producing a more spherical ventricle.

Difference between end-diastolic and end-systolic sphericity index, SIed - SIes

*d*σ

\*p < 0.05.

Values are mean ± SD.

Based on Table 10, increased LV contractile function *d*

(b) Post-SVR ED & ES

Fig. 13. 3-dimensional reconstructions during end-diastole (panels A and C) and end-systole (panels B and D) phases before (panels A and B) and after (panels C and D) SVR using LVtools. It is created from the endocardial and epicardial contours, which were drawn for calculations of ventricular volumes and function from the multiple short-axis cines (Figure 12). This figure is based on our work presented in Ref. 19.

Fig. 14. Changes in end-diastolic volume (EDV), end-systolic volume (ESV), LVEF and contractility index *d*σ*\*/dtmax* after SVR. This figure is adopted from our work in Ref. 19.

Fig. 15. Association between *d*σ*\*/dtmax* and left ventricular (LV) ejection fraction (EF) pre- and post-SVR. (Solid line: *d*σ*\*/dtmax*=9.045×EF+1.091, r=0.69, p<0.001 for pre-SVR; dash line: *d*σ*\*/dtmax*=9.969×EF+1.337, r=0.77, p<0.001 for post-SVR). This figure is adopted from our work in Ref 19.
