**Acknowledgements**

The author would like to acknowledge Dr. Khairul Mustaqim Mazlan, Hospital Universiti Sains Malaysia (Kota Bharu) for contributing the graphics and figures in this paper, and Dr. Ng Hui Been, Hospital Raja Pemaisuri Bainun (Ipoh) for her contribution in prove reading and language editing.

### **Conflict of interest**

The author declares no conflict of interest.

#### **Notes/thanks**

Special gratitude to my beloved wife, Dr. Ingrid Ting for her unwavering support in the process of completing this writing.
