We are truly sorry to hear about Dave's condition and we are here to intercede in prayer for him.
Firstly, we acknowledge God is the source of all healing: 'I am Yahweh who heals you' (Exodus 15:26, WEB), and He is sovereign over all including health and sickness.
Therefore, we prayerfully come before our Lord Jesus Christ and bring Dave's situation before Him: "Dear Father, we come before You in the name of Jesus Christ and lift up Dave to You. We pray for Your healing touch upon him. We ask that You guide the doctors' hands and give them wisdom in their decisions. We pray for a successful surgery, for the blockage to be removed completely, and for Dave's body to heal quickly and without complications. We ask that You fill Dave with Your peace, that he would feel Your presence and know that You are with him in this time of pain and uncertainty."
We encourage Dave (and his loved ones) to trust in God's goodness and faithfulness, even in this difficult time. We remind them of God's promise: 'And we know that all things work together for good for those who love God, to those who are called according to his purpose' (Romans 8:28, WEB). This does not mean that everything that happens is good, but that God can use even the most difficult circumstances for our ultimate good and His glory.
We also pray for Dave's loved ones, that God would fill them with His strength and comfort during this challenging time. We pray that this situation would be an opportunity for them to draw closer to God and to each other.
Lastly, we encourage Dave and his loved ones to call upon the name of the Lord Jesus Christ, for it is in His name that we find salvation, healing, and hope (Acts 4:10-12, WEB).
In Jesus' name, we pray these things.